Initial Jack import.

Change-Id: I953cf0a520195a7187d791b2885848ad0d5a9b43

127 files changed, 12083 insertions, 0 deletions

diff --git a/watchmaker/examples/examples.iml b/watchmaker/examples/examples.iml
new file mode 100644
index 0000000..6f94484
--- /dev/null
+++ b/watchmaker/examples/examples.iml
@@ -0,0 +1,33 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<module org.jetbrains.idea.maven.project.MavenProjectsManager.isMavenModule="true" type="JAVA_MODULE" version="4">
+  <component name="NewModuleRootManager" LANGUAGE_LEVEL="JDK_1_6" inherit-compiler-output="false">
+    <output url="file://$MODULE_DIR$/target/classes" />
+    <output-test url="file://$MODULE_DIR$/target/test-classes" />
+    <exclude-output />
+    <content url="file://$MODULE_DIR$">
+      <sourceFolder url="file://$MODULE_DIR$/src/java/main" isTestSource="false" />
+      <sourceFolder url="file://$MODULE_DIR$/src/java/resources" isTestSource="false" />
+      <sourceFolder url="file://$MODULE_DIR$/src/java/test" isTestSource="true" />
+      <excludeFolder url="file://$MODULE_DIR$/target" />
+    </content>
+    <orderEntry type="inheritedJdk" />
+    <orderEntry type="sourceFolder" forTests="false" />
+    <orderEntry type="module" module-name="swing" />
+    <orderEntry type="module" module-name="framework" />
+    <orderEntry type="library" name="Maven: org.uncommons.maths:uncommons-maths:1.2.2" level="project" />
+    <orderEntry type="library" name="Maven: jfree:jcommon:1.0.12" level="project" />
+    <orderEntry type="library" name="Maven: jfree:jfreechart:1.0.13" level="project" />
+    <orderEntry type="library" name="Maven: com.google.collections:google-collections:1.0" level="project" />
+    <orderEntry type="library" scope="TEST" name="Maven: org.testng:testng:6.2.1" level="project" />
+    <orderEntry type="library" scope="TEST" name="Maven: junit:junit:3.8.1" level="project" />
+    <orderEntry type="library" scope="TEST" name="Maven: org.beanshell:bsh:2.0b4" level="project" />
+    <orderEntry type="library" scope="TEST" name="Maven: com.beust:jcommander:1.12" level="project" />
+    <orderEntry type="library" scope="TEST" name="Maven: org.yaml:snakeyaml:1.6" level="project" />
+    <orderEntry type="library" scope="TEST" name="Maven: org.easytesting:fest-swing:1.2.1" level="project" />
+    <orderEntry type="library" scope="TEST" name="Maven: org.easytesting:fest-assert:1.2" level="project" />
+    <orderEntry type="library" scope="TEST" name="Maven: org.easytesting:fest-util:1.1.3" level="project" />
+    <orderEntry type="library" scope="TEST" name="Maven: org.easytesting:fest-reflect:1.2" level="project" />
+    <orderEntry type="library" scope="TEST" name="Maven: net.jcip:jcip-annotations:1.0" level="project" />
+  </component>
+</module>
+
diff --git a/watchmaker/examples/nb-configuration.xml b/watchmaker/examples/nb-configuration.xml
new file mode 100644
index 0000000..ae35717
--- /dev/null
+++ b/watchmaker/examples/nb-configuration.xml
@@ -0,0 +1,61 @@
+<?xml version="1.0" encoding="UTF-8"?>

+<project-shared-configuration>

+    <!--
+This file contains additional configuration written by modules in the NetBeans IDE.
+The configuration is intended to be shared among all the users of project and
+therefore it is assumed to be part of version control checkout.
+Without this configuration present, some functionality in the IDE may be limited or fail altogether.
+-->

+    <properties xmlns="http://www.netbeans.org/ns/maven-properties-data/1">

+        <!--
+Properties that influence various parts of the IDE, especially code formatting and the like. 
+You can copy and paste the single properties, into the pom.xml file and the IDE will pick them up.
+That way multiple projects can share the same settings (useful for formatting rules for example).
+Any value defined here will override the pom.xml file value but is only applicable to the current project.
+-->

+        <org-netbeans-modules-editor-indent.CodeStyle.usedProfile>project</org-netbeans-modules-editor-indent.CodeStyle.usedProfile>

+        <org-netbeans-modules-editor-indent.CodeStyle.project.spaces-per-tab>2</org-netbeans-modules-editor-indent.CodeStyle.project.spaces-per-tab>

+        <org-netbeans-modules-editor-indent.CodeStyle.project.tab-size>2</org-netbeans-modules-editor-indent.CodeStyle.project.tab-size>

+        <org-netbeans-modules-editor-indent.CodeStyle.project.indent-shift-width>2</org-netbeans-modules-editor-indent.CodeStyle.project.indent-shift-width>

+        <org-netbeans-modules-editor-indent.CodeStyle.project.expand-tabs>false</org-netbeans-modules-editor-indent.CodeStyle.project.expand-tabs>

+        <org-netbeans-modules-editor-indent.CodeStyle.project.text-limit-width>100</org-netbeans-modules-editor-indent.CodeStyle.project.text-limit-width>

+        <org-netbeans-modules-editor-indent.CodeStyle.project.text-line-wrap>words</org-netbeans-modules-editor-indent.CodeStyle.project.text-line-wrap>

+        <org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.blankLinesAfterClassHeader>0</org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.blankLinesAfterClassHeader>

+        <org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.wrapExtendsImplementsKeyword>WRAP_IF_LONG</org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.wrapExtendsImplementsKeyword>

+        <org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.redundantIfBraces>LEAVE_ALONE</org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.redundantIfBraces>

+        <org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.redundantForBraces>LEAVE_ALONE</org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.redundantForBraces>

+        <org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.spaceBeforeColon>false</org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.spaceBeforeColon>

+        <org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.wrapTryResources>WRAP_IF_LONG</org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.wrapTryResources>

+        <org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.wrapMethodParams>WRAP_IF_LONG</org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.wrapMethodParams>

+        <org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.wrapTernaryOps>WRAP_IF_LONG</org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.wrapTernaryOps>

+        <org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.wrapThrowsKeyword>WRAP_IF_LONG</org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.wrapThrowsKeyword>

+        <org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.spaces-per-tab>2</org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.spaces-per-tab>

+        <org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.wrapAssignOps>WRAP_IF_LONG</org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.wrapAssignOps>

+        <org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.placeElseOnNewLine>true</org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.placeElseOnNewLine>

+        <org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.wrapEnumConstants>WRAP_IF_LONG</org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.wrapEnumConstants>

+        <org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.placeFinallyOnNewLine>true</org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.placeFinallyOnNewLine>

+        <org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.placeCatchOnNewLine>true</org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.placeCatchOnNewLine>

+        <org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.classDeclBracePlacement>NEW_LINE</org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.classDeclBracePlacement>

+        <org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.wrapMethodCallArgs>WRAP_IF_LONG</org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.wrapMethodCallArgs>

+        <org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.wrapDisjunctiveCatchTypes>WRAP_IF_LONG</org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.wrapDisjunctiveCatchTypes>

+        <org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.wrapChainedMethodCalls>WRAP_IF_LONG</org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.wrapChainedMethodCalls>

+        <org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.wrapFor>WRAP_IF_LONG</org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.wrapFor>

+        <org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.wrapArrayInit>WRAP_IF_LONG</org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.wrapArrayInit>

+        <org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.wrapAssert>WRAP_IF_LONG</org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.wrapAssert>

+        <org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.wrapBinaryOps>WRAP_IF_LONG</org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.wrapBinaryOps>

+        <org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.wrapAnnotationArgs>WRAP_IF_LONG</org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.wrapAnnotationArgs>

+        <org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.indent-shift-width>2</org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.indent-shift-width>

+        <org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.placeWhileOnNewLine>true</org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.placeWhileOnNewLine>

+        <org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.text-limit-width>100</org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.text-limit-width>

+        <org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.wrapExtendsImplementsList>WRAP_IF_LONG</org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.wrapExtendsImplementsList>

+        <org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.generateParagraphTagOnBlankLines>true</org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.generateParagraphTagOnBlankLines>

+        <org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.redundantWhileBraces>LEAVE_ALONE</org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.redundantWhileBraces>

+        <org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.tab-size>2</org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.tab-size>

+        <org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.continuationIndentSize>2</org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.continuationIndentSize>

+        <org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.expand-tabs>false</org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.expand-tabs>

+        <org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.otherBracePlacement>NEW_LINE</org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.otherBracePlacement>

+        <org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.methodDeclBracePlacement>NEW_LINE</org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.methodDeclBracePlacement>

+        <org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.redundantDoWhileBraces>LEAVE_ALONE</org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.redundantDoWhileBraces>

+        <org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.wrapThrowsList>WRAP_IF_LONG</org-netbeans-modules-editor-indent.text.x-java.CodeStyle.project.wrapThrowsList>

+    </properties>

+</project-shared-configuration>

diff --git a/watchmaker/examples/pom.xml b/watchmaker/examples/pom.xml
new file mode 100644
index 0000000..773b7d2
--- /dev/null
+++ b/watchmaker/examples/pom.xml
@@ -0,0 +1,58 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--===========================================================================
+  Copyright 2006-2010 Daniel W. Dyer
+
+  Licensed under the Apache License, Version 2.0 (the "License");
+  you may not use this file except in compliance with the License.
+  You may obtain a copy of the License at
+
+      http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+  ==========================================================================-->
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
+
+	<modelVersion>4.0.0</modelVersion>
+	<parent>
+		<groupId>org.uncommons.watchmaker</groupId>
+		<artifactId>watchmaker</artifactId>
+		<version>0.7.2</version>
+	</parent>
+	<artifactId>watchmaker-examples</artifactId>
+
+	<dependencies>
+		<dependency>
+			<groupId>${project.groupId}</groupId>
+			<artifactId>watchmaker-swing</artifactId>
+			<version>${project.version}</version>
+		</dependency>
+		<dependency>
+			<groupId>org.testng</groupId>
+			<artifactId>testng</artifactId>
+			<version>6.2.1</version>
+			<scope>test</scope>
+		</dependency>
+		<dependency>
+			<groupId>org.easytesting</groupId>
+			<artifactId>fest-swing</artifactId>
+			<version>1.2.1</version>
+			<scope>test</scope>
+		</dependency>
+	</dependencies>  
+	
+	<build>
+		<sourceDirectory>src/java/main</sourceDirectory>
+		<testSourceDirectory>src/java/test</testSourceDirectory>
+		<resources>
+			<resource>
+				<directory>src/java/resources</directory>
+			</resource>
+		</resources>
+	</build>
+</project>
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/AbstractExampleApplet.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/AbstractExampleApplet.java
new file mode 100644
index 0000000..8bf600a
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/AbstractExampleApplet.java
@@ -0,0 +1,102 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples;
+
+import java.awt.Container;
+import java.lang.reflect.InvocationTargetException;
+import javax.swing.JApplet;
+import javax.swing.JFrame;
+import javax.swing.JOptionPane;
+import javax.swing.SwingUtilities;
+import javax.swing.UIManager;
+
+/**
+ * Base class for examples that run as applets.
+ * @author Daniel Dyer
+ */
+public abstract class AbstractExampleApplet extends JApplet
+{
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+    public void init()
+    {
+        configure(this);
+    }
+
+
+    /**
+     * Configure the program to display its GUI in the specified container.
+     * @param container The container to place the GUI components in.
+     */
+    private void configure(final Container container)
+    {
+        try
+        {
+            // Use invokeAndWait so that we can be sure that initialisation is complete
+            // before continuing.
+            SwingUtilities.invokeAndWait(new Runnable()
+            {
+                public void run()
+                {
+                    try
+                    {
+                        UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
+                    }
+                    catch (Exception ex)
+                    {
+                        // This should never happen as we are installing a known look-and-feel.
+                        System.err.println("Failed to load System look-and-feel.");
+                    }
+                    prepareGUI(container);
+                }
+            });
+        }
+        catch (InterruptedException ex)
+        {
+            // Restore interrupt flag.
+            Thread.currentThread().interrupt();
+        }
+        catch (InvocationTargetException ex)
+        {
+            ex.getCause().printStackTrace();
+            JOptionPane.showMessageDialog(container, ex.getCause(), "Error Occurred", JOptionPane.ERROR_MESSAGE);
+        }
+    }
+
+
+    /**
+     * Implemented in sub-classes to initialise and layout the GUI.
+     * @param container The container that this method should add components to.
+     */
+    protected abstract void prepareGUI(Container container);
+
+
+    /**
+     * Display this example program using a JFrame as the top-level GUI container (rather
+     * than running the example as an applet).
+     * @param title The text to use for the frame's title bar.
+     */
+    protected void displayInFrame(String title)
+    {
+        JFrame frame = new JFrame(title);
+        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
+        configure(frame);
+        frame.pack();
+        frame.setVisible(true);
+    }
+}
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/EvolutionLogger.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/EvolutionLogger.java
new file mode 100644
index 0000000..5c47146
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/EvolutionLogger.java
@@ -0,0 +1,39 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples;
+
+import org.uncommons.watchmaker.framework.PopulationData;
+import org.uncommons.watchmaker.framework.islands.IslandEvolutionObserver;
+
+/**
+ * Trivial evolution observer for displaying information at the end
+ * of each generation.
+ * @param <T> The type of entity being evolved.
+ * @author Daniel Dyer
+ */
+public class EvolutionLogger<T> implements IslandEvolutionObserver<T>
+{
+    public void populationUpdate(PopulationData<? extends T> data)
+    {
+        System.out.println("Generation " + data.getGenerationNumber() + ": " + data.getBestCandidateFitness());
+    }
+
+
+    public void islandPopulationUpdate(int islandIndex, PopulationData<? extends T> populationData)
+    {
+        // Do nothing.
+    }
+}
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/Launcher.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/Launcher.java
new file mode 100644
index 0000000..b4b5b7e
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/Launcher.java
@@ -0,0 +1,79 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples;
+
+import java.lang.reflect.Method;
+import java.util.Arrays;
+import java.util.LinkedHashMap;
+import java.util.Map;
+import org.uncommons.util.reflection.ReflectionUtils;
+import org.uncommons.watchmaker.examples.biomorphs.BiomorphApplet;
+import org.uncommons.watchmaker.examples.bits.BitsExample;
+import org.uncommons.watchmaker.examples.geneticprogramming.GeneticProgrammingExample;
+import org.uncommons.watchmaker.examples.monalisa.MonaLisaApplet;
+import org.uncommons.watchmaker.examples.strings.StringsExample;
+import org.uncommons.watchmaker.examples.sudoku.SudokuApplet;
+import org.uncommons.watchmaker.examples.travellingsalesman.TravellingSalesmanApplet;
+
+/**
+ * Launcher for Watchmaker example applications.
+ * @author Daniel Dyer
+ */
+public class Launcher
+{
+    private static final Map<String, Class<?>> EXAMPLES = new LinkedHashMap<String, Class<?>>();
+    static
+    {
+        EXAMPLES.put("biomorphs", BiomorphApplet.class);
+        EXAMPLES.put("bits", BitsExample.class);
+        EXAMPLES.put("gp", GeneticProgrammingExample.class);
+        EXAMPLES.put("monalisa", MonaLisaApplet.class);
+        EXAMPLES.put("salesman", TravellingSalesmanApplet.class);
+        EXAMPLES.put("strings", StringsExample.class);
+        EXAMPLES.put("sudoku", SudokuApplet.class);
+    }
+
+
+    private Launcher()
+    {
+        // Prevents instantiation of launcher class.
+    }
+
+    
+    /**
+     * Launch the specified example application from the command-line.
+     * @param args First item is the name of the example to run.  Any subsequent arguments are passed
+     * on to the specific example.
+     */
+    public static void main(String[] args)
+    {
+        Class<?> exampleClass = args.length > 0 ? EXAMPLES.get(args[0]) : null;
+        if (exampleClass == null)
+        {
+            System.err.println("First argument must be the name of an example, i.e. one of "
+                               + Arrays.toString(EXAMPLES.keySet().toArray()));
+            System.exit(1);
+        }
+
+        // All args except the first one should be passed to the example application.
+        String[] appArgs = new String[args.length - 1];
+        System.arraycopy(args, 1, appArgs, 0, appArgs.length);
+
+        // Invoke the main method for the selected example application.
+        Method main = ReflectionUtils.findKnownMethod(exampleClass, "main", String[].class);
+        ReflectionUtils.invokeUnchecked(main, exampleClass, new Object[]{appArgs});
+    }
+}
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/biomorphs/Biomorph.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/biomorphs/Biomorph.java
new file mode 100644
index 0000000..7fe6fd5
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/biomorphs/Biomorph.java
@@ -0,0 +1,160 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.biomorphs;
+
+import java.util.Arrays;
+
+/**
+ * <p>Candidate representation for a biomorph.  We could just as easily have
+ * used an array of integers or a bit string representation with Gray codes
+ * but for clarity we will use this more object-oriented representation that
+ * conveniently combines state and related logic.</p>
+ *
+ * <p>The Biomporph class encapsulates 9 genes as described by Dawkins in his
+ * "The Evolution of Evolvability" paper.</p>
+ *
+ * @author Daniel Dyer
+ */
+public final class Biomorph
+{
+    /** The total number of genes that make up a biomorph. */
+    public static final int GENE_COUNT = 9;
+    /** The minimum permitted value for most genes. */
+    public static final int GENE_MIN = -5;
+    /** The maximum permitted value for most genes. */
+    public static final int GENE_MAX = 5;
+    /** The index of the gene that controls biomporph size. */
+    public static final int LENGTH_GENE_INDEX = 8;
+    /** The minimum permitted value for the length gene. */
+    public static final int LENGTH_GENE_MIN = 1;
+    /** The maximum permitted value for the length gene. */
+    public static final int LENGTH_GENE_MAX = 7;
+
+    private final int[] genes;
+
+    private int[][] phenotype;
+
+
+    /**
+     * Creates a biomorph with the specified genes.
+     * @param genes A 9-element array.  The final element must be a positive
+     * value.
+     */
+    public Biomorph(int[] genes)
+    {
+        if (genes.length != GENE_COUNT)
+        {
+            throw new IllegalArgumentException("Biomorph must have " + GENE_COUNT + " genes.");
+        }
+        this.genes = genes.clone();
+    }
+
+
+    /**
+     * Returns an array of integers that represent the graphical pattern
+     * determined by the biomorph's genes.
+     * @return A 2-dimensional array containing the 8-element dx and dy
+     * arrays required to draw the biomorph.
+     */
+    public int[][] getPatternPhenotype()
+    {
+        if (phenotype == null)
+        {
+            // Decode the genes as per Dawkins' rules.
+            int[] dx = new int[GENE_COUNT - 1];
+            dx[3] = genes[0];
+            dx[4] = genes[1];
+            dx[5] = genes[2];
+
+            dx[1] = -dx[3];
+            dx[0] = -dx[4];
+            dx[7] = -dx[5];
+
+            dx[2] = 0;
+            dx[6] = 0;
+
+            int[] dy = new int[GENE_COUNT - 1];
+            dy[2] = genes[3];
+            dy[3] = genes[4];
+            dy[4] = genes[5];
+            dy[5] = genes[6];
+            dy[6] = genes[7];
+
+            dy[0] = dy[4];
+            dy[1] = dy[3];
+            dy[7] = dy[5];
+
+            phenotype = new int[][]{dx, dy};
+        }
+        return phenotype;
+    }
+
+
+    /**
+     * @return The value of the gene that controls the size of this biomorph.
+     */
+    public int getLengthPhenotype()
+    {
+        return genes[LENGTH_GENE_INDEX];
+    }
+
+
+    /**
+     * Returns the 9 genes that make up the biomorph's genotype. 
+     * @return A 9-element array containing this biomorph's genes.
+     */
+    public int[] getGenotype()
+    {
+        return genes.clone();
+    }
+
+
+    /**
+     * Compares the genes of two Biomporph objects and returns true if they are
+     * identical.
+     * @param obj The object to compare with this one.
+     * @return True if the argument is a Biomoprh instance and the 2
+     * biomorphs have the same genes, false otherwise.
+     */
+    @Override
+    public boolean equals(Object obj)
+    {
+        if (this == obj)
+        {
+            return true;
+        }
+        if (obj == null || getClass() != obj.getClass())
+        {
+            return false;
+        }
+
+        Biomorph biomorph = (Biomorph) obj;
+
+        return Arrays.equals(genes, biomorph.genes);
+    }
+
+
+    /**
+     * Over-ridden to be consistent with {@link #equals(Object)}.  Biomorphs
+     * with identical genes return identical hash codes.
+     * @return This object's hash code.
+     */
+    @Override
+    public int hashCode()
+    {
+        return Arrays.hashCode(genes);
+    }
+}
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/biomorphs/BiomorphApplet.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/biomorphs/BiomorphApplet.java
new file mode 100644
index 0000000..0766422
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/biomorphs/BiomorphApplet.java
@@ -0,0 +1,241 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.biomorphs;
+
+import java.awt.BorderLayout;
+import java.awt.Container;
+import java.awt.FlowLayout;
+import java.awt.GridLayout;
+import java.awt.event.ActionEvent;
+import java.awt.event.ActionListener;
+import java.awt.event.ItemEvent;
+import java.awt.event.ItemListener;
+import javax.swing.BorderFactory;
+import javax.swing.JButton;
+import javax.swing.JComboBox;
+import javax.swing.JComponent;
+import javax.swing.JDialog;
+import javax.swing.JFrame;
+import javax.swing.JLabel;
+import javax.swing.JPanel;
+import javax.swing.JSpinner;
+import javax.swing.SpinnerNumberModel;
+import javax.swing.SpringLayout;
+import javax.swing.SwingUtilities;
+import org.uncommons.maths.random.MersenneTwisterRNG;
+import org.uncommons.maths.random.Probability;
+import org.uncommons.swing.SpringUtilities;
+import org.uncommons.swing.SwingBackgroundTask;
+import org.uncommons.watchmaker.examples.AbstractExampleApplet;
+import org.uncommons.watchmaker.framework.EvolutionEngine;
+import org.uncommons.watchmaker.framework.EvolutionObserver;
+import org.uncommons.watchmaker.framework.EvolutionaryOperator;
+import org.uncommons.watchmaker.framework.GenerationalEvolutionEngine;
+import org.uncommons.watchmaker.framework.PopulationData;
+import org.uncommons.watchmaker.framework.interactive.InteractiveSelection;
+import org.uncommons.watchmaker.framework.interactive.Renderer;
+import org.uncommons.watchmaker.framework.termination.GenerationCount;
+import org.uncommons.watchmaker.swing.SwingConsole;
+
+/**
+ * Watchmaker Framework implementation of Dawkin's biomorph program.
+ * @author Daniel Dyer
+ */
+public class BiomorphApplet extends AbstractExampleApplet
+{
+    private Renderer<Biomorph, JComponent> renderer;
+    private SwingConsole console;
+    private JDialog selectionDialog;
+    private JPanel biomorphHolder;
+
+
+    /**
+     * Initialise and layout the GUI.
+     * @param container The Swing component that will contain the GUI controls.
+     */
+    @Override
+    protected void prepareGUI(Container container)
+    {
+        renderer = new SwingBiomorphRenderer();
+        console = new SwingConsole(5);
+        selectionDialog = new JDialog((JFrame) null, "Biomorph Selection", true);
+        biomorphHolder = new JPanel(new GridLayout(1, 1));
+
+        container.add(new ControlPanel(), BorderLayout.WEST);
+        container.add(biomorphHolder, BorderLayout.CENTER);
+        biomorphHolder.setBorder(BorderFactory.createTitledBorder("Last Evolved Biomorph"));
+        biomorphHolder.add(new JLabel("Nothing generated yet.", JLabel.CENTER));
+        selectionDialog.add(console, BorderLayout.CENTER);
+        selectionDialog.setSize(800, 600);
+        selectionDialog.validate();
+    }
+
+
+    /**
+     * Helper method to create a background task for running the interactive evolutionary
+     * algorithm.
+     * @param populationSize How big the population used by the created evolution engine
+     * should be.
+     * @param generationCount How many generations to use when the evolution engine is
+     * invoked.
+     * @param random If true use random mutation, otherwise use Dawkins mutation.
+     * @return A Swing task that will execute on a background thread and update
+     * the GUI when it is done.
+     */
+    private SwingBackgroundTask<Biomorph> createTask(final int populationSize,
+                                                     final int generationCount,
+                                                     final boolean random)
+    {
+        return new SwingBackgroundTask<Biomorph>()
+        {
+            @Override
+            protected Biomorph performTask()
+            {
+                EvolutionaryOperator<Biomorph> mutation = random ? new RandomBiomorphMutation(new Probability(0.12d))
+                                                                 : new DawkinsBiomorphMutation();
+                InteractiveSelection<Biomorph> selection = new InteractiveSelection<Biomorph>(console,
+                                                                                              renderer,
+                                                                                              populationSize,
+                                                                                              1);
+                EvolutionEngine<Biomorph> engine = new GenerationalEvolutionEngine<Biomorph>(new BiomorphFactory(),
+                                                                                             mutation,
+                                                                                             selection,
+                                                                                             new MersenneTwisterRNG());
+                engine.addEvolutionObserver(new GenerationTracker());
+                return engine.evolve(populationSize,
+                                     0,
+                                     new GenerationCount(generationCount));
+            }
+
+            @Override
+            protected void postProcessing(Biomorph result)
+            {
+                selectionDialog.setVisible(false);
+                biomorphHolder.removeAll();
+                biomorphHolder.add(renderer.render(result));
+                biomorphHolder.revalidate();
+            }
+        };
+    }
+
+
+    /**
+     * Entry point for running this example as an application rather than an applet.
+     * @param args Program arguments (ignored).
+     */
+    public static void main(String[] args)
+    {
+        new BiomorphApplet().displayInFrame("Watchmaker Framework - Biomporphs Example");
+    }
+
+
+    /**
+     * Simple observer to update the dialog title every time the evolution advances
+     * to a new generation.
+     */
+    private final class GenerationTracker implements EvolutionObserver<Biomorph>
+    {
+        public void populationUpdate(final PopulationData<? extends Biomorph> populationData)
+        {
+            SwingUtilities.invokeLater(new Runnable()
+            {
+                public void run()
+                {
+                    selectionDialog.setTitle("Biomorph Selection - Generation "
+                                             + (populationData.getGenerationNumber() + 1));
+                }
+            });
+        }
+    }
+
+
+    /**
+     * Panel for controlling the evolutionary algorithm parameters.
+     */
+    private final class ControlPanel extends JPanel
+    {
+        private JSpinner populationSpinner;
+        private JSpinner generationsSpinner;
+        private JComboBox mutationCombo;
+
+        ControlPanel()
+        {
+            super(new BorderLayout());
+            add(createInputPanel(), BorderLayout.NORTH);
+            add(createButtonPanel(), BorderLayout.SOUTH);
+            setBorder(BorderFactory.createTitledBorder("Evolution Controls"));
+        }
+
+
+        private JComponent createInputPanel()
+        {
+            JPanel inputPanel = new JPanel(new SpringLayout());
+            JLabel populationLabel = new JLabel("Population Size: ");
+            populationSpinner = new JSpinner(new SpinnerNumberModel(18, 2, 25, 1));
+            populationSpinner.setEnabled(false);
+            populationLabel.setLabelFor(populationSpinner);
+            inputPanel.add(populationLabel);
+            inputPanel.add(populationSpinner);
+            JLabel generationsLabel = new JLabel("Number of Generations: ");
+            generationsSpinner = new JSpinner(new SpinnerNumberModel(20, 1, 100, 1));
+            generationsLabel.setLabelFor(generationsSpinner);
+            inputPanel.add(generationsLabel);
+            inputPanel.add(generationsSpinner);
+            JLabel mutationLabel = new JLabel("Mutation Type: ");
+            mutationCombo = new JComboBox(new String[]{"Dawkins (Non-random)", "Random"});
+            mutationCombo.addItemListener(new ItemListener()
+            {
+                public void itemStateChanged(ItemEvent itemEvent)
+                {
+                    if (mutationCombo.getSelectedIndex() == 0)
+                    {
+                        populationSpinner.setValue(18);
+                        populationSpinner.setEnabled(false);
+                    }
+                    else
+                    {
+                        populationSpinner.setEnabled(true);
+                    }
+                }
+            });
+            inputPanel.add(mutationLabel);
+            inputPanel.add(mutationCombo);
+
+            SpringUtilities.makeCompactGrid(inputPanel, 3, 2, 30, 6, 6, 6);
+
+            return inputPanel;
+        }
+
+
+        private JComponent createButtonPanel()
+        {
+            JPanel buttonPanel = new JPanel(new FlowLayout(FlowLayout.RIGHT));
+            JButton startButton = new JButton("Start");
+            startButton.addActionListener(new ActionListener()
+            {
+                public void actionPerformed(ActionEvent actionEvent)
+                {
+                    createTask((Integer) populationSpinner.getValue(),
+                               (Integer) generationsSpinner.getValue(),
+                               mutationCombo.getSelectedIndex() == 1).execute();
+                    selectionDialog.setVisible(true);
+                }
+            });
+            buttonPanel.add(startButton);
+            return buttonPanel;
+        }
+    }
+}
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/biomorphs/BiomorphFactory.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/biomorphs/BiomorphFactory.java
new file mode 100644
index 0000000..d081e40
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/biomorphs/BiomorphFactory.java
@@ -0,0 +1,44 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.biomorphs;
+
+import java.util.Random;
+import org.uncommons.watchmaker.framework.factories.AbstractCandidateFactory;
+
+/**
+ * Candidate factory for creating random biomorphs.
+ * @author Daniel Dyer
+ */
+public class BiomorphFactory extends AbstractCandidateFactory<Biomorph>
+{
+    /**
+     * Generates a random biomorph by providing a random value for each gene.
+     * @param rng The source of randomness used to generate the biomoprh. 
+     * @return A randomly-generated biomorph.
+     */
+    public Biomorph generateRandomCandidate(Random rng)
+    {
+        int[] genes = new int[Biomorph.GENE_COUNT];
+        for (int i = 0; i < Biomorph.GENE_COUNT - 1; i++)
+        {
+            // First 8 genes have values between -5 and 5.
+            genes[i] = rng.nextInt(11) - 5;
+        }
+        // Last genes ha a value between 1 and 7.
+        genes[Biomorph.LENGTH_GENE_INDEX] = rng.nextInt(Biomorph.LENGTH_GENE_MAX) + 1;
+        return new Biomorph(genes);
+    }
+}
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/biomorphs/DawkinsBiomorphMutation.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/biomorphs/DawkinsBiomorphMutation.java
new file mode 100644
index 0000000..f718a76
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/biomorphs/DawkinsBiomorphMutation.java
@@ -0,0 +1,67 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.biomorphs;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Random;
+import org.uncommons.watchmaker.framework.EvolutionaryOperator;
+
+/**
+ * Non-random mutation of a population of biomorphs.  This ensures that each selected candidate
+ * is mutated differently.  This is the mutation used by Dawkins in his original experiment.
+ * @author Daniel Dyer
+ */
+public class DawkinsBiomorphMutation implements EvolutionaryOperator<Biomorph>
+{
+    /**
+     * Mutate a population of biomorphs non-randomly, ensuring that each selected
+     * candidate is mutated differently. 
+     * @param selectedCandidates {@inheritDoc}
+     * @param rng A source of randomness (not used since this mutation is non-random).
+     * @return {@inheritDoc}
+     */
+    public List<Biomorph> apply(List<Biomorph> selectedCandidates, Random rng)
+    {
+        List<Biomorph> mutatedPopulation = new ArrayList<Biomorph>(selectedCandidates.size());
+        int mutatedGene = 0;
+        int mutation = 1;
+        for (Biomorph b : selectedCandidates)
+        {
+            int[] genes = b.getGenotype();
+
+            mutation *= -1; // Alternate between incrementing and decrementing.
+            if (mutation == 1) // After gene has been both incremented and decremented, move to next one.
+            {
+                mutatedGene = (mutatedGene + 1) % Biomorph.GENE_COUNT;
+            }
+            genes[mutatedGene] += mutation;
+            int min = mutatedGene == Biomorph.LENGTH_GENE_INDEX ? Biomorph.LENGTH_GENE_MIN : Biomorph.GENE_MIN;
+            int max = mutatedGene == Biomorph.LENGTH_GENE_INDEX ? Biomorph.LENGTH_GENE_MAX : Biomorph.GENE_MAX;
+            if (genes[mutatedGene] > max)
+            {
+                genes[mutatedGene] = min;
+            }
+            else if (genes[mutatedGene] < min)
+            {
+                genes[mutatedGene] = max;
+            }
+
+            mutatedPopulation.add(new Biomorph(genes));
+        }
+        return mutatedPopulation;
+    }
+}
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/biomorphs/RandomBiomorphMutation.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/biomorphs/RandomBiomorphMutation.java
new file mode 100644
index 0000000..a98cb55
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/biomorphs/RandomBiomorphMutation.java
@@ -0,0 +1,98 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.biomorphs;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Random;
+import org.uncommons.maths.random.Probability;
+import org.uncommons.watchmaker.framework.EvolutionaryOperator;
+
+/**
+ * Mutation operator for biomorphs.  Mutates each individual gene
+ * according to some mutation probability.
+ * @author Daniel Dyer
+ */
+public class RandomBiomorphMutation implements EvolutionaryOperator<Biomorph>
+{
+    private final Probability mutationProbability;
+
+    /**
+     * @param mutationProbability The probability that a given gene
+     * is changed.
+     */
+    public RandomBiomorphMutation(Probability mutationProbability)
+    {
+        this.mutationProbability = mutationProbability;
+    }
+
+
+    /**
+     * Randomly mutate each selected candidate.
+     * @param selectedCandidates {@inheritDoc}
+     * @param rng {@inheritDoc}
+     * @return {@inheritDoc}
+     */
+    public List<Biomorph> apply(List<Biomorph> selectedCandidates, Random rng)
+    {
+        List<Biomorph> mutatedPopulation = new ArrayList<Biomorph>(selectedCandidates.size());
+        for (Biomorph biomorph : selectedCandidates)
+        {
+            mutatedPopulation.add(mutateBiomorph(biomorph, rng));
+        }
+        return mutatedPopulation;
+    }
+
+
+    /**
+     * Mutates a single biomorph.
+     * @param biomorph The biomorph to mutate.
+     * @param rng The source of randomness to use for mutation.
+     * @return A mutated version of the biomorph.
+     */
+    private Biomorph mutateBiomorph(Biomorph biomorph, Random rng)
+    {
+        int[] genes = biomorph.getGenotype();
+        assert genes.length == Biomorph.GENE_COUNT : "Biomorphs must have " + Biomorph.GENE_COUNT + " genes.";
+        for (int i = 0; i < Biomorph.GENE_COUNT - 1; i++)
+        {
+            if (mutationProbability.nextEvent(rng))
+            {
+                boolean increase = rng.nextBoolean();
+                genes[i] += (increase ? 1 : -1);
+                if (genes[i] > Biomorph.GENE_MAX)
+                {
+                    genes[i] = Biomorph.GENE_MIN;
+                }
+                else if (genes[i] < Biomorph.GENE_MIN)
+                {
+                    genes[i] = Biomorph.GENE_MAX;
+                }
+            }
+        }
+        boolean increase = rng.nextBoolean();
+        genes[Biomorph.LENGTH_GENE_INDEX] += (increase ? 1 : -1);
+        if (genes[Biomorph.LENGTH_GENE_INDEX] > Biomorph.LENGTH_GENE_MAX)
+        {
+            genes[Biomorph.LENGTH_GENE_INDEX] = Biomorph.LENGTH_GENE_MIN;
+        }
+        else if (genes[Biomorph.LENGTH_GENE_INDEX] < Biomorph.LENGTH_GENE_MIN)
+        {
+            genes[Biomorph.LENGTH_GENE_INDEX] = Biomorph.LENGTH_GENE_MAX;
+        }
+        return new Biomorph(genes);
+    }
+}
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/biomorphs/SwingBiomorphRenderer.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/biomorphs/SwingBiomorphRenderer.java
new file mode 100644
index 0000000..d6d8e82
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/biomorphs/SwingBiomorphRenderer.java
@@ -0,0 +1,111 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.biomorphs;
+
+import java.awt.Dimension;
+import java.awt.Graphics;
+import java.awt.Graphics2D;
+import java.awt.RenderingHints;
+import javax.swing.JComponent;
+import org.uncommons.watchmaker.framework.interactive.Renderer;
+
+/**
+ * Renders Biomorphs as Swing components.
+ * @author Daniel Dyer
+ */
+public class SwingBiomorphRenderer implements Renderer<Biomorph, JComponent>
+{
+    /**
+     * Renders an evolved biomorph as a component that can be displayed
+     * in a Swing GUI.
+     * @param biomorph The biomorph to render.
+     * @return A component that displays a visual representation of the
+     * biomorph.
+     */
+    public JComponent render(Biomorph biomorph)
+    {
+        return new BiomorphView(biomorph);
+    }
+
+
+    /**
+     * A Swing component that can display a visual representation of a
+     * biomorph.
+     */
+    private static final class BiomorphView extends JComponent
+    {
+        private final Biomorph biomorph;
+
+        BiomorphView(Biomorph biomorph)
+        {
+            this.biomorph = biomorph;
+            Dimension size = new Dimension(200, 200);
+            setMinimumSize(size);
+            setPreferredSize(size);
+        }
+
+
+        @Override
+        protected void paintComponent(Graphics graphics)
+        {
+            super.paintComponent(graphics);
+            if (graphics instanceof Graphics2D)
+            {
+                ((Graphics2D) graphics).setRenderingHint(RenderingHints.KEY_ANTIALIASING,
+                                                         RenderingHints.VALUE_ANTIALIAS_ON);
+            }
+
+            int[][] pattern = biomorph.getPatternPhenotype();
+            int depth = biomorph.getLengthPhenotype();
+
+            drawTree(graphics,
+                     getSize().width / 2,
+                     getSize().height / 2,
+                     depth,
+                     2, // Initial direction should be 2 or 6 to ensure horizontal symmetry.
+                     pattern[0], // dx
+                     pattern[1]); // dy
+        }
+
+
+        /**
+         * Recursive method for drawing tree branches.
+         */
+        private void drawTree(Graphics graphics,
+                              int x,
+                              int y,
+                              int length,
+                              int direction,
+                              int[] dx,
+                              int[] dy)
+        {
+            // Make sure direction wraps round in the range 0 - 7.
+            direction = (direction + 8) % 8;
+
+            int x2 = x + length * dx[direction];
+            int y2 = y + length * dy[direction];
+
+            graphics.drawLine(x, y, x2, y2);
+
+            if (length > 0)
+            {
+                // Recursively draw the left and right branches of the tree.
+                drawTree(graphics, x2, y2, length - 1, direction - 1, dx, dy);
+                drawTree(graphics, x2, y2, length - 1, direction + 1, dx, dy);
+            }
+        }
+    }
+}
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/biomorphs/package-info.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/biomorphs/package-info.java
new file mode 100644
index 0000000..1f73010
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/biomorphs/package-info.java
@@ -0,0 +1,21 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+/**
+ * An evolutionary simulation along the lines of the Biomporph program described
+ * by Richard Dawkins in his book, The Blind Watchmaker.
+ * @author Daniel Dyer
+ */
+package org.uncommons.watchmaker.examples.biomorphs;
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/bits/BitStringEvaluator.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/bits/BitStringEvaluator.java
new file mode 100644
index 0000000..3a6421c
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/bits/BitStringEvaluator.java
@@ -0,0 +1,51 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.bits;
+
+import java.util.List;
+import org.uncommons.maths.binary.BitString;
+import org.uncommons.watchmaker.framework.FitnessEvaluator;
+
+/**
+ * A fitness evaluator that simply counts the number of ones in a bit
+ * string.
+ * @see BitString
+ * @author Daniel Dyer
+ */
+public class BitStringEvaluator implements FitnessEvaluator<BitString>
+{
+    /**
+     * Calculates a fitness score for the candidate bit string.
+     * @param candidate The evolved bit string to evaluate.
+     * @param population {@inheritDoc}
+     * @return How many bits in the string are set to 1.
+     */
+    public double getFitness(BitString candidate,
+                             List<? extends BitString> population)
+    {
+        return candidate.countSetBits();
+    }
+
+
+    /**
+     * Always returns true.  A higher score indicates a fitter individual.
+     * @return True.
+     */
+    public boolean isNatural()
+    {
+        return true;
+    }
+}
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/bits/BitsExample.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/bits/BitsExample.java
new file mode 100644
index 0000000..4b6a1c8
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/bits/BitsExample.java
@@ -0,0 +1,67 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.bits;
+
+import java.util.ArrayList;
+import java.util.List;
+import org.uncommons.maths.binary.BitString;
+import org.uncommons.maths.random.MersenneTwisterRNG;
+import org.uncommons.maths.random.Probability;
+import org.uncommons.watchmaker.examples.EvolutionLogger;
+import org.uncommons.watchmaker.framework.EvolutionaryOperator;
+import org.uncommons.watchmaker.framework.GenerationalEvolutionEngine;
+import org.uncommons.watchmaker.framework.factories.BitStringFactory;
+import org.uncommons.watchmaker.framework.operators.BitStringCrossover;
+import org.uncommons.watchmaker.framework.operators.BitStringMutation;
+import org.uncommons.watchmaker.framework.operators.EvolutionPipeline;
+import org.uncommons.watchmaker.framework.selection.RouletteWheelSelection;
+import org.uncommons.watchmaker.framework.termination.TargetFitness;
+
+/**
+ * An implementation of the first exercise (page 31) from the book An Introduction to
+ * Genetic Algorithms, by Melanie Mitchell.  The algorithm evolves bit strings and the
+ * fitness function simply counts the number of ones in the bit string.  The evolution
+ * should therefore converge on strings that consist only of ones.
+ * @author Daniel Dyer
+ */
+public class BitsExample
+{
+    private static final int BITS = 20;
+
+    public static void main(String[] args)
+    {
+        evolveBits(BITS);
+    }
+
+
+    public static BitString evolveBits(int length)
+    {
+        List<EvolutionaryOperator<BitString>> operators = new ArrayList<EvolutionaryOperator<BitString>>(2);
+        operators.add(new BitStringCrossover(1, new Probability(0.7d)));
+        operators.add(new BitStringMutation(new Probability(0.01d)));
+        EvolutionaryOperator<BitString> pipeline = new EvolutionPipeline<BitString>(operators);
+        GenerationalEvolutionEngine<BitString> engine = new GenerationalEvolutionEngine<BitString>(new BitStringFactory(length),
+                                                                                                   pipeline,
+                                                                                                   new BitStringEvaluator(),
+                                                                                                   new RouletteWheelSelection(),
+                                                                                                   new MersenneTwisterRNG());
+        engine.setSingleThreaded(true); // Performs better for very trivial fitness evaluations.
+        engine.addEvolutionObserver(new EvolutionLogger<BitString>());
+        return engine.evolve(100, // 100 individuals in each generation.
+                             0, // Don't use elitism.
+                             new TargetFitness(length, true)); // Continue until a perfect match is found.        
+    }
+}
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/bits/package-info.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/bits/package-info.java
new file mode 100644
index 0000000..058458b
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/bits/package-info.java
@@ -0,0 +1,23 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+/**
+ * An implementation of the first exercise from the book An Introduction to Genetic
+ * Algorithms, by Melanie Mitchell.  The algorithm evolves bit strings and the
+ * fitness function simply counts the number of ones in the bit string.  The evolution
+ * should therefore converge on strings that consist only of ones.
+ * @author Daniel Dyer
+ */
+package org.uncommons.watchmaker.examples.bits;
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/geneticprogramming/Addition.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/geneticprogramming/Addition.java
new file mode 100644
index 0000000..641510c
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/geneticprogramming/Addition.java
@@ -0,0 +1,79 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.geneticprogramming;
+
+/**
+ * Simple addition operator {@link Node}.
+ * @author Daniel Dyer
+ */
+public class Addition extends BinaryNode
+{
+    /**
+     * Creates a node that evaluates to the sum of the values of its two
+     * child nodes ({@literal left} and {@literal right}).
+     * @param left The first operand.
+     * @param right The second operand.
+     */
+    public Addition(Node left, Node right)
+    {
+        super(left, right, '+');
+    }
+
+
+    /**
+     * Evaluates the two sub-trees and returns the sum of these two values.
+     * @param programParameters Program parameters (ignored by the addition operator
+     * but may be used in evaluating the sub-trees).
+     * @return The sum of the values of both child nodes.
+     */
+    public double evaluate(double[] programParameters)
+    {
+        return left.evaluate(programParameters) + right.evaluate(programParameters);
+    }
+
+
+    /**
+     * {@inheritDoc}
+     */
+    public Node simplify()
+    {
+        Node simplifiedLeft = left.simplify();
+        Node simplifiedRight = right.simplify();
+        // Adding zero is pointless, the expression can be reduced to its other argument.
+        if (simplifiedRight instanceof Constant && simplifiedRight.evaluate(NO_ARGS) == 0)
+        {
+            return simplifiedLeft;
+        }
+        else if (simplifiedLeft instanceof Constant && simplifiedLeft.evaluate(NO_ARGS) == 0)
+        {
+            return simplifiedRight;
+        }
+        // If the two arguments are constants, we can simplify by calculating the result, it won't
+        // ever change.
+        else if (simplifiedLeft instanceof Constant && simplifiedRight instanceof Constant)
+        {
+            return new Constant(simplifiedLeft.evaluate(NO_ARGS) + simplifiedRight.evaluate(NO_ARGS));
+        }
+        else if (simplifiedLeft != left || simplifiedRight != right)
+        {
+            return new Addition(simplifiedLeft, simplifiedRight);
+        }
+        else
+        {
+            return this;
+        }
+    }
+}
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/geneticprogramming/BinaryNode.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/geneticprogramming/BinaryNode.java
new file mode 100644
index 0000000..2273f74
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/geneticprogramming/BinaryNode.java
@@ -0,0 +1,214 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.geneticprogramming;
+
+import java.lang.reflect.Constructor;
+import java.util.Random;
+import org.uncommons.maths.random.Probability;
+import org.uncommons.util.reflection.ReflectionUtils;
+
+/**
+ * Convenient base class for {@link Node}s that have two sub-trees.
+ * @author Daniel Dyer
+ */
+abstract class BinaryNode implements Node
+{
+    protected static final double[] NO_ARGS = new double[0];
+
+    /** The first argument to the binary function. */
+    protected final Node left;
+    /** The second argument to the binary function. */
+    protected final Node right;
+    
+    private final char symbol;
+
+
+    /**
+     * @param left The first argument to the binary function.
+     * @param right The second argument to the binary function.
+     * @param symbol A single character that indicates the type of function.
+     */
+    protected BinaryNode(Node left, Node right, char symbol)
+    {
+        this.left = left;
+        this.right = right;
+        this.symbol = symbol;
+    }
+
+
+    /**
+     * {@inheritDoc}
+     */
+    public String getLabel()
+    {
+        return String.valueOf(symbol);
+    }
+
+
+    /**
+     * The arity of a binary node is two.
+     * @return 2
+     */
+    public int getArity()
+    {
+        return 2;
+    }
+
+
+    /**
+     * The depth of a binary node is the depth of its deepest sub-tree plus one.
+     * @return The depth of the tree rooted at this node.
+     */
+    public int getDepth()
+    {
+        return 1 + Math.max(left.getDepth(), right.getDepth());
+    }
+
+
+    /**
+     * The width of a binary node is the sum of the widths of its two sub-trees.
+     * @return The width of the tree rooted at this node.
+     */
+    public int getWidth()
+    {
+        return left.getWidth() + right.getWidth();
+    }
+
+
+    /**
+     * {@inheritDoc}
+     */
+    public int countNodes()
+    {
+        return 1 + left.countNodes() + right.countNodes();
+    }
+
+
+    /**
+     * {@inheritDoc}
+     */
+    public Node getNode(int index)
+    {
+        if (index == 0)
+        {
+            return this;
+        }
+        int leftNodes = left.countNodes();
+        if (index <= leftNodes)
+        {
+            return left.getNode(index - 1);
+        }
+        else
+        {
+            return right.getNode(index - leftNodes - 1);
+        }
+    }
+
+
+    /**
+     * {@inheritDoc}
+     */
+    public Node getChild(int index)
+    {
+        switch (index)
+        {
+            case 0: return left;
+            case 1: return right;
+            default: throw new IndexOutOfBoundsException("Invalid child index: " + index);
+        }
+    }
+
+
+    /**
+     * {@inheritDoc}
+     */
+    public Node replaceNode(int index, Node newNode)
+    {
+        if (index == 0)
+        {
+            return newNode;
+        }
+
+        int leftNodes = left.countNodes();
+        if (index <= leftNodes)
+        {
+            return newInstance(left.replaceNode(index - 1, newNode), right);
+        }
+        else
+        {
+            return newInstance(left, right.replaceNode(index - leftNodes - 1, newNode));
+        }
+    }
+
+
+
+    /**
+     * {@inheritDoc} 
+     */
+    public String print()
+    {
+        StringBuilder buffer = new StringBuilder("(");
+        buffer.append(left.print());
+        buffer.append(' ');
+        buffer.append(symbol);
+        buffer.append(' ');
+        buffer.append(right.print());
+        buffer.append(')');
+        return buffer.toString();
+    }
+
+
+    /**
+     * {@inheritDoc}
+     */
+    public Node mutate(Random rng, Probability mutationProbability, TreeFactory treeFactory)
+    {
+        if (mutationProbability.nextEvent(rng))
+        {
+            return treeFactory.generateRandomCandidate(rng);
+        }
+        else
+        {
+            Node newLeft = left.mutate(rng, mutationProbability, treeFactory);
+            Node newRight = right.mutate(rng, mutationProbability, treeFactory);
+            if (newLeft != left && newRight != right)
+            {
+                return newInstance(newLeft, newRight);
+            }
+            else
+            {
+                // Tree has not changed.
+                return this;
+            }
+        }
+    }
+
+
+    private Node newInstance(Node newLeft, Node newRight)
+    {
+        Constructor<? extends BinaryNode> constructor = ReflectionUtils.findKnownConstructor(this.getClass(),
+                                                                                             Node.class,
+                                                                                             Node.class);
+        return ReflectionUtils.invokeUnchecked(constructor, newLeft, newRight);
+    }
+
+
+    @Override
+    public String toString()
+    {
+        return print();
+    }
+}
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/geneticprogramming/Constant.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/geneticprogramming/Constant.java
new file mode 100644
index 0000000..2a07538
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/geneticprogramming/Constant.java
@@ -0,0 +1,101 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.geneticprogramming;
+
+import java.text.DecimalFormat;
+
+/**
+ * A program node that evaluates to a constant value. 
+ * @author Daniel Dyer
+ */
+public class Constant extends LeafNode
+{
+    private static final DecimalFormat NUMBER_FORMAT = new DecimalFormat("######0.##");
+
+    private final double constant;
+    private final String label;
+
+
+    /**
+     * Creates a constant-valued node. 
+     * @param constant The value that this node will always evaluate to.
+     */
+    public Constant(double constant)
+    {
+        this.constant = constant;
+        this.label = NUMBER_FORMAT.format(constant);
+    }
+
+
+    /**
+     * @param programParameters The parameters passed to the program (ignored by this node).
+     * @return The numeric value of this constant.
+     */
+    public double evaluate(double[] programParameters)
+    {
+        return constant;
+    }
+
+
+    /**
+     * {@inheritDoc}
+     */
+    public String getLabel()
+    {
+        return label;
+    }
+
+
+    /**
+     * @return The String representation of this constant.
+     */
+    public String print()
+    {
+        return String.valueOf(constant);
+    }
+
+
+    /**
+     * Two constants are equal if they have the same numeric value.
+     * @param other The object that this object is compared to.
+     * @return True if the constants are equivalent, false otherwise.
+     */
+    @Override
+    public boolean equals(Object other)
+    {
+        if (this == other)
+        {
+            return true;
+        }
+        if (other == null || getClass() != other.getClass())
+        {
+            return false;
+        }
+        return Double.compare(((Constant) other).constant, constant) == 0;
+    }
+
+
+    /**
+     * Over-ridden to be consistent with {@link #equals(Object)}.
+     * @return This object's hash code.
+     */
+    @Override
+    public int hashCode()
+    {
+        long temp = constant != +0.0d ? Double.doubleToLongBits(constant) : 0L;
+        return (int) (temp ^ (temp >>> 32));
+    }
+}
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/geneticprogramming/GeneticProgrammingExample.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/geneticprogramming/GeneticProgrammingExample.java
new file mode 100644
index 0000000..c060d49
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/geneticprogramming/GeneticProgrammingExample.java
@@ -0,0 +1,85 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.geneticprogramming;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import org.uncommons.maths.random.MersenneTwisterRNG;
+import org.uncommons.maths.random.Probability;
+import org.uncommons.watchmaker.examples.EvolutionLogger;
+import org.uncommons.watchmaker.framework.EvolutionEngine;
+import org.uncommons.watchmaker.framework.EvolutionaryOperator;
+import org.uncommons.watchmaker.framework.GenerationalEvolutionEngine;
+import org.uncommons.watchmaker.framework.operators.EvolutionPipeline;
+import org.uncommons.watchmaker.framework.selection.RouletteWheelSelection;
+import org.uncommons.watchmaker.framework.termination.TargetFitness;
+
+/**
+ * Simple tree-based genetic programming application based on the first example
+ * in Chapter 11 of Toby Segaran's Programming Collective Intelligence.
+ * @author Daniel Dyer
+ */
+public class GeneticProgrammingExample
+{
+    // This data describes the problem.  For each pair of inputs, the generated program
+    // should return the associated output.  The goal of this appliction is to generalise
+    // the examples into an equation.
+    private static final Map<double[], Double> TEST_DATA = new HashMap<double[], Double>();
+    static
+    {
+        TEST_DATA.put(new double[]{26, 35}, 829.0d);
+        TEST_DATA.put(new double[]{8, 24}, 141.0d);
+        TEST_DATA.put(new double[]{20, 1}, 467.0d);
+        TEST_DATA.put(new double[]{33, 11}, 1215.0d);
+        TEST_DATA.put(new double[]{37, 16}, 1517.0d);
+    }
+
+
+    public static void main(String[] args)
+    {
+        Node program = evolveProgram(TEST_DATA);
+        System.out.println(program.print());
+    }
+
+
+    /**
+     * Evolve a function to fit the specified data.
+     * @param data A map from input values to expected output values.
+     * @return A program that generates the correct outputs for all specified
+     * sets of input.
+     */
+    public static Node evolveProgram(Map<double[], Double> data)
+    {
+        TreeFactory factory = new TreeFactory(2, // Number of parameters passed into each program.
+                                              4, // Maximum depth of generated trees.
+                                              Probability.EVENS, // Probability that a node is a function node.
+                                              new Probability(0.6d)); // Probability that other nodes are params rather than constants.
+        List<EvolutionaryOperator<Node>> operators = new ArrayList<EvolutionaryOperator<Node>>(3);
+        operators.add(new TreeMutation(factory, new Probability(0.4d)));
+        operators.add(new TreeCrossover());
+        operators.add(new Simplification());
+        TreeEvaluator evaluator = new TreeEvaluator(data);
+        EvolutionEngine<Node> engine = new GenerationalEvolutionEngine<Node>(factory,
+                                                                             new EvolutionPipeline<Node>(operators),
+                                                                             evaluator,
+                                                                             new RouletteWheelSelection(),
+                                                                             new MersenneTwisterRNG());
+        engine.addEvolutionObserver(new EvolutionLogger<Node>());
+        return engine.evolve(1000, 5, new TargetFitness(0d, evaluator.isNatural()));
+    }
+}
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/geneticprogramming/IfThenElse.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/geneticprogramming/IfThenElse.java
new file mode 100644
index 0000000..54abc4c
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/geneticprogramming/IfThenElse.java
@@ -0,0 +1,268 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.geneticprogramming;
+
+import java.util.Random;
+import org.uncommons.maths.random.Probability;
+
+/**
+ * Simple conditional program {@link Node}.
+ * @author Daniel Dyer
+ */
+public class IfThenElse implements Node
+{
+    private final Node condition;
+    private final Node then;
+    private final Node otherwise;
+
+    /**
+     * @param condition If this node evaluates to a value greater than zero then
+     * the value of the {@literal then} node is returned.  Otherwise the value of
+     * the {@literal otherwise} node is returned.
+     * @param then This node is evaluated if the {@literal condition} node has a
+     * value greater than zero.
+     * @param otherwise This node is evaluated if the {@literal condition} node has a
+     * value less than or equal to zero.
+     */
+    public IfThenElse(Node condition, Node then, Node otherwise)
+    {
+        this.condition = condition;
+        this.then = then;
+        this.otherwise = otherwise;
+    }
+
+
+    /**
+     * {@inheritDoc}
+     */
+    public String getLabel()
+    {
+        return "if";
+    }
+
+
+    /**
+     * The arity of a ternary node is three.
+     * @return 3
+     */
+    public int getArity()
+    {
+        return 3;
+    }
+
+
+    /**
+     * {@inheritDoc}
+     */
+    public int getDepth()
+    {
+        return 1 + Math.max(condition.getDepth(), Math.max(then.getDepth(), otherwise.getDepth()));
+    }
+
+
+    /**
+     * {@inheritDoc}
+     */
+    public int getWidth()
+    {
+        return condition.getWidth() + then.getWidth() + otherwise.getWidth();
+    }
+
+
+    /**
+     * {@inheritDoc}
+     */
+    public int countNodes()
+    {
+        return 1 + condition.countNodes() + then.countNodes() + otherwise.countNodes();
+    }
+
+
+    /**
+     * {@inheritDoc}
+     */
+    public Node getNode(int index)
+    {
+        if (index == 0)
+        {
+            return this;
+        }
+        int conditionNodes = condition.countNodes();
+        if (index <= conditionNodes)
+        {
+            return condition.getNode(index - 1);
+        }
+        else
+        {
+            int thenNodes = then.countNodes();
+            if (index <= conditionNodes + thenNodes)
+            {
+                return then.getNode(index - conditionNodes - 1);
+            }
+            else
+            {
+                return otherwise.getNode(index - conditionNodes - thenNodes - 1);
+            }
+        }
+    }
+
+
+    /**
+     * {@inheritDoc}
+     */
+    public Node getChild(int index)
+    {
+        switch (index)
+        {
+            case 0: return condition;
+            case 1: return then;
+            case 2 : return otherwise;
+            default: throw new IndexOutOfBoundsException("Invalid child index: " + index);
+        }
+    }
+
+
+
+    /**
+     * {@inheritDoc}
+     */
+    public Node replaceNode(int index, Node newNode)
+    {
+        if (index == 0)
+        {
+            return newNode;
+        }
+
+        int conditionNodes = condition.countNodes();
+        if (index <= conditionNodes)
+        {
+            return new IfThenElse(condition.replaceNode(index - 1, newNode), then, otherwise);
+        }
+        else
+        {
+            int thenNodes = then.countNodes();
+            if (index <= conditionNodes + thenNodes)
+            {
+                return new IfThenElse(condition, then.replaceNode(index - conditionNodes - 1, newNode), otherwise);
+            }
+            else
+            {
+                return new IfThenElse(condition,
+                                      then,
+                                      otherwise.replaceNode(index - conditionNodes - thenNodes - 1, newNode));
+            }
+        }
+    }
+
+
+
+    /**
+     * {@inheritDoc}
+     * Operates on three other nodes.  The first is an expression to evaluate.
+     * Which of the other two nodes is evaluated and returned depends on whether
+     * this node evaluates to greater than zero or not.
+     * @param programParameters Program parameters (ignored by the conditional operator
+     * but may be used in evaluating child nodes).
+     */
+    public double evaluate(double[] programParameters)
+    {
+        return condition.evaluate(programParameters) > 0 // If...
+               ? then.evaluate(programParameters)   // Then...
+               : otherwise.evaluate(programParameters);  // Else...
+    }
+
+    
+    /**
+     * {@inheritDoc}
+     */
+    public String print()
+    {
+        return "(" + condition.print() + " ? " + then.print() + " : " + otherwise.print() + ")";
+    }
+
+
+    /**
+     * {@inheritDoc}
+     */    
+    public Node mutate(Random rng, Probability mutationProbability, TreeFactory treeFactory)
+    {
+        if (mutationProbability.nextEvent(rng))
+        {
+            return treeFactory.generateRandomCandidate(rng);
+        }
+        else
+        {
+            Node newCondition = condition.mutate(rng, mutationProbability, treeFactory);
+            Node newThen = then.mutate(rng, mutationProbability, treeFactory);
+            Node newOtherwise = otherwise.mutate(rng, mutationProbability, treeFactory);
+            if (newCondition != condition || newThen != then || newOtherwise != otherwise)
+            {
+                return new IfThenElse(newCondition, newThen, newOtherwise);
+            }
+            else
+            {
+                // Tree has not changed.
+                return this;
+            }
+        }
+
+    }
+
+
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+    public String toString()
+    {
+        return print();
+    }
+
+
+    /**
+     * {@inheritDoc}
+     */
+    public Node simplify()
+    {
+        Node simplifiedCondition = condition.simplify();
+
+        // If the condition is constant then the expression can be replaced by the branch that
+        // always gets evaluated.
+        if (simplifiedCondition instanceof Constant)
+        {
+            return simplifiedCondition.evaluate(null) > 0 ? then.simplify() : otherwise.simplify();
+        }
+        else
+        {
+            Node simplifiedThen = then.simplify();
+            Node simplifiedOtherwise = otherwise.simplify();
+            // If both branches are identical, the condition is irrelevant.
+            if (simplifiedThen.equals(simplifiedOtherwise))
+            {
+                return simplifiedThen;
+            }
+            // Only create a new node if something has actually changed, otherwise return the existing node.
+            if (simplifiedCondition != condition || simplifiedThen != then || simplifiedOtherwise != otherwise)
+            {
+                return new IfThenElse(simplifiedCondition, simplifiedThen, simplifiedOtherwise);
+            }
+            else
+            {
+                return this;
+            }
+        }
+    }
+}
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/geneticprogramming/IsGreater.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/geneticprogramming/IsGreater.java
new file mode 100644
index 0000000..bd23472
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/geneticprogramming/IsGreater.java
@@ -0,0 +1,78 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.geneticprogramming;
+
+/**
+ * A program {@link Node} that evaluates to a one if the value of its first
+ * argument is greater than the value of its second, or evaluates to zero otherwise. 
+ * @author Daniel Dyer
+ */
+public class IsGreater extends BinaryNode
+{
+    /**
+     * Creates a node that evaluates to one if the value of the first child node
+     * is greater than the value of the second child node.  Otherwise it evaluates
+     * to zero.
+     * @param left The first operand.
+     * @param right The second operand.
+     */
+    public IsGreater(Node left, Node right)
+    {
+        super(left, right, '>');
+    }
+
+
+    /**
+     * Returns a value of one if the value of the first node is greater than the value of
+     * the second node.  Returns a value of zero otherwise.
+     * @param programParameters The parameters passed to this program (ignored by the
+     * IsGreater node but may be used in the evaluation of child nodes).
+     * @return One or zero depending on the relative values of the two child nodes.
+     */
+    public double evaluate(double[] programParameters)
+    {
+        return left.evaluate(programParameters) > right.evaluate(programParameters) ? 1 : 0;
+    }
+
+
+    /**
+     * {@inheritDoc}
+     */
+    public Node simplify()
+    {
+        Node simplifiedLeft = left.simplify();
+        Node simplifiedRight = right.simplify();
+        // If the two arguments are exactly equivalent, one cannot be greater than the other.
+        if (simplifiedLeft.equals(simplifiedRight))
+        {
+            return new Constant(0);
+        }
+        // If the two arguments are constants, we can simplify by calculating the result, it won't
+        // ever change.
+        else if (simplifiedLeft instanceof Constant && simplifiedRight instanceof Constant)
+        {
+            return new Constant(simplifiedLeft.evaluate(NO_ARGS) > simplifiedRight.evaluate(NO_ARGS) ? 1 : 0);
+        }
+        else if (simplifiedLeft != left || simplifiedRight != right)
+        {
+            return new IsGreater(simplifiedLeft, simplifiedRight);
+        }
+        else
+        {
+            return this;
+        }
+    }
+}
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/geneticprogramming/LeafNode.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/geneticprogramming/LeafNode.java
new file mode 100644
index 0000000..cf8718a
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/geneticprogramming/LeafNode.java
@@ -0,0 +1,127 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.geneticprogramming;
+
+import java.util.Random;
+import org.uncommons.maths.random.Probability;
+
+/**
+ * Convenient base class for {@link Node}s that have no sub-trees.
+ * @author Daniel Dyer
+ */
+abstract class LeafNode implements Node
+{
+    /**
+     * The arity of a non-function node is always zero.
+     * @return 0
+     */
+    public int getArity()
+    {
+        return 0;
+    }
+
+    
+    /**
+     * Leaf nodes always have a depth of 1 since they have no child nodes.
+     * @return 1 
+     */
+    public int getDepth()
+    {
+        return 1;
+    }
+
+
+    /**
+     * Leaf nodes always have a width of 1 since they have no child nodes.
+     * @return 1
+     */
+    public int getWidth()
+    {
+        return 1;
+    }
+
+    
+    /**
+     * {@inheritDoc}
+     */
+    public int countNodes()
+    {
+        return 1;
+    }
+
+
+    public Node getNode(int index)
+    {
+        if (index != 0)
+        {
+            throw new IndexOutOfBoundsException("Invalid node index: " + index);
+        }
+        return this;
+    }
+
+
+    /**
+     * {@inheritDoc}
+     */
+    public Node getChild(int index)
+    {
+        throw new IndexOutOfBoundsException("Leaf nodes have no children.");
+    }
+
+
+    public Node replaceNode(int index, Node newNode)
+    {
+        if (index != 0)
+        {
+            throw new IndexOutOfBoundsException("Invalid node index: " + index);
+        }
+        return newNode;        
+    }
+
+    
+    /**
+     * {@inheritDoc}
+     */
+    public Node mutate(Random rng, Probability mutationProbability, TreeFactory treeFactory)
+    {
+        if (mutationProbability.nextEvent(rng))
+        {
+            return treeFactory.generateRandomCandidate(rng);
+        }
+        else
+        {
+            // Node is unchanged.
+            return this;
+        }
+    }
+
+
+    @Override
+    public String toString()
+    {
+        return print();
+    }
+
+
+    /**
+     * Returns this node (leaf nodes cannot be simplified).
+     * @return This node, unmodified.
+     */
+    public Node simplify()
+    {
+        return this;
+    }
+}
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/geneticprogramming/Multiplication.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/geneticprogramming/Multiplication.java
new file mode 100644
index 0000000..bd5dd60
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/geneticprogramming/Multiplication.java
@@ -0,0 +1,90 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.geneticprogramming;
+
+/**
+ * Simple multiplication operator {@link Node}.
+ * @author Daniel Dyer
+ */
+public class Multiplication extends BinaryNode
+{
+    /**
+     * Creates a node that evaluates to the product of the values of its two
+     * child nodes ({@literal left} and {@literal right}).
+     * @param left The first operand.
+     * @param right The second operand.
+     */
+    public Multiplication(Node left, Node right)
+    {
+        super(left, right, '*');
+    }
+
+
+    /**
+     * Evaluates the two sub-trees and returns the product of these two values.
+     * @param programParameters Program parameters (ignored by the multiplication operator
+     * but may be used in evaluating the sub-trees).
+     * @return The sum of the values of both child nodes.
+     */
+    public double evaluate(double[] programParameters)
+    {
+        return left.evaluate(programParameters) * right.evaluate(programParameters);
+    }
+
+
+    /**
+     * {@inheritDoc}
+     */
+    public Node simplify()
+    {
+        Node simplifiedLeft = left.simplify();
+        Node simplifiedRight = right.simplify();
+        // If the two arguments are constants, we can simplify by calculating the result, it won't
+        // ever change.
+        if (simplifiedLeft instanceof Constant && simplifiedRight instanceof Constant)
+        {
+            return new Constant(simplifiedLeft.evaluate(NO_ARGS) * simplifiedRight.evaluate(NO_ARGS));
+        }
+        // Multiplying by one is pointless, the expression can be reduced to its other argument.
+        else if (simplifiedRight instanceof Constant)
+        {
+            double constant = simplifiedRight.evaluate(NO_ARGS);
+            if (constant == 1)
+            {
+                return simplifiedLeft;
+            }
+            else if (constant == 0)
+            {
+                return new Constant(0);
+            }
+        }
+        else if (simplifiedLeft instanceof Constant)
+        {
+            double constant = simplifiedLeft.evaluate(NO_ARGS);
+            if (constant == 1)
+            {
+                return simplifiedRight;
+            }
+            else if (constant == 0)
+            {
+                return new Constant(0);
+            }
+        }
+        return simplifiedLeft != left || simplifiedRight != right
+               ? new Multiplication(simplifiedLeft, simplifiedRight)
+               : this;
+    }
+}
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/geneticprogramming/Node.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/geneticprogramming/Node.java
new file mode 100644
index 0000000..7df1685
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/geneticprogramming/Node.java
@@ -0,0 +1,120 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.geneticprogramming;
+
+import java.util.Random;
+import org.uncommons.maths.random.Probability;
+
+/**
+ * Operations supported by the different types of nodes that make up
+ * genetic program trees.
+ * @author Daniel Dyer
+ */
+public interface Node
+{
+    /**
+     * Recursively evaluates the (sub-)tree represented by this node (including any
+     * child nodes) and returns a numeric value.
+     * @param programParameters Program parameters (possibly used by this node and/or
+     * in the evaluation of child nodes).
+     * @return The result of evaluating this node and all of its children.
+     */
+    double evaluate(double[] programParameters);
+
+    /**
+     * Recursively builds a string representation of the tree rooted at this node.
+     * @return A string representation of this tree.
+     */
+    String print();
+
+    /**
+     * @return A short String that represents the function or value represented by this node.
+     */
+    String getLabel();
+
+    /**
+     * If this is a function (non-leaf) node, how many arguments does it take?  For
+     * leaf nodes the answer is zero.
+     * @return The arity of this function, or zero if this node is a leaf node.
+     * @see #countNodes()
+     */
+    int getArity();
+
+    /**
+     * @return The number of levels of nodes that make up this tree.
+     * @see #getWidth()
+     */
+    int getDepth();
+
+    /**
+     * Work out how wide (in nodes) this tree is.  Used primarily for laying out a
+     * visual representation.  A leaf node has a width of 1.  A binary node's width
+     * is the sum of the widths of its sub-trees.
+     * @return The maximum width of this tree.
+     * @see #getDepth()
+     * @see #getArity()
+     */
+    int getWidth();
+
+    /**
+     * @return The total number of nodes in this tree (recursively counts the nodes
+     * for each sub-node of this node).
+     * @see #getArity() 
+     */
+    int countNodes();
+
+    /**
+     * Retrieves a sub-node from this tree. 
+     * @param index The index of a node.  Index 0 is the root node.  Nodes are numbered
+     * depth-first, right-to-left.
+     * @return The node at the specified position.
+     */
+    Node getNode(int index);
+
+    /**
+     * Retrieves a direct sub-node from this tree.
+     * @param index The index of a child node.  Index 0 is the first child.  Nodes are numbered
+     * right-to-left, grandchild nodes are not included.
+     * @return The node at the specified position.
+     */
+    Node getChild(int index);
+
+    /**
+     * Returns a new tree that is identical to this tree except with the specified node
+     * replaced. 
+     * @param index The index of the node to replace.
+     * @param newNode The replacement node.
+     * @return A new tree with the node at the specified index replaced by
+     * {@code newNode}.
+     */
+    Node replaceNode(int index, Node newNode);
+
+    /**
+     * Helper method for the {@link TreeMutation} evolutionary operator.
+     * @param rng A source of randomness.
+     * @param mutationProbability The probability that a given node will be mutated.
+     * @param treeFactory A factory for creating the new sub-trees needed for mutation.
+     * @return The mutated node (or the same node if no mutation occurred).
+     */
+    Node mutate(Random rng, Probability mutationProbability, TreeFactory treeFactory);
+
+    /**
+     * Reduce this program tree to its simplest equivalent form.
+     * @return A simplification of this program tree, or this program tree unodified if it
+     * cannot be simplified.
+     */
+    Node simplify();
+}
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/geneticprogramming/Parameter.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/geneticprogramming/Parameter.java
new file mode 100644
index 0000000..575bd1d
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/geneticprogramming/Parameter.java
@@ -0,0 +1,102 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.geneticprogramming;
+
+/**
+ * A program {@link Node} that simply returns the value of one of the
+ * program's parameters.
+ * @author Daniel Dyer
+ */
+public class Parameter extends LeafNode
+{
+    private final int parameterIndex;
+
+    /**
+     * @param parameterIndex Which of the program's (zero-indexed) parameter
+     * values should be returned upon evaluation of this node.
+     */
+    public Parameter(int parameterIndex)
+    {
+        this.parameterIndex = parameterIndex;
+    }
+
+
+    /**
+     * Returns the value of one of the program parameters.
+     * @param programParameters The parameters to this program.
+     * @return The program parameter at the index condigured for this node.
+     */
+    public double evaluate(double[] programParameters)
+    {
+        if (parameterIndex >= programParameters.length)
+        {
+            throw new IllegalArgumentException("Invalid parameter index: " + parameterIndex);
+        }
+        return programParameters[parameterIndex];
+    }
+
+
+    /**
+     * {@inheritDoc}
+     */
+    public String getLabel()
+    {
+        return "P" + parameterIndex;
+    }
+
+
+    /**
+     * {@inheritDoc}
+     * For a parameter node the String representation is simply "arg0", "arg1", etc.
+     * depending on which program parameter it refers to.
+     */
+    public String print()
+    {
+        return "arg" + parameterIndex;
+    }
+
+
+    /**
+     * Two parameters are equal if they evaluate to the same program argument
+     * (i.e. they have the same parameter index).
+     * @param other The object that this object is compared to.
+     * @return True if the parameters are equivalent, false otherwise.
+     */
+    @Override
+    public boolean equals(Object other)
+    {
+        if (this == other)
+        {
+            return true;
+        }
+        if (other == null || getClass() != other.getClass())
+        {
+            return false;
+        }
+        return parameterIndex == ((Parameter) other).parameterIndex;
+    }
+
+
+    /**
+     * Over-ridden to be consistent with {@link #equals(Object)}.
+     * @return This object's hash code.
+     */
+    @Override
+    public int hashCode()
+    {
+        return parameterIndex;
+    }
+}
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/geneticprogramming/Simplification.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/geneticprogramming/Simplification.java
new file mode 100644
index 0000000..f44864b
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/geneticprogramming/Simplification.java
@@ -0,0 +1,71 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.geneticprogramming;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Random;
+import org.uncommons.maths.random.Probability;
+import org.uncommons.watchmaker.framework.EvolutionaryOperator;
+
+/**
+ * Evolutionary operator for GP trees that reduces them to their simplest form.
+ * @author Daniel Dyer
+ */
+public class Simplification implements EvolutionaryOperator<Node>
+{
+    private final Probability probability;
+
+
+    /**
+     * Creates a simplification operator with a probability of 1 (i.e. all
+     * canidates will be simplified).
+     */
+    public Simplification()
+    {
+        this(Probability.ONE);
+    }
+
+
+    /**
+     * Creates a simplfication operator that has the specified probability of being
+     * applied to any individual candidate. 
+     * @param probability The probability that this operator will attempt to simplify
+     * any single expression.
+     */
+    public Simplification(Probability probability)
+    {
+        this.probability = probability;
+    }
+
+
+    /**
+     * Simplify the expressions represented by the candidates.  Each expression
+     * is simplified according to the configured probability.
+     * @param selectedCandidates The individuals to evolve.
+     * @param rng A source of randomness.
+     * @return The (possibly) simplified candidates.
+     */
+    public List<Node> apply(List<Node> selectedCandidates, Random rng)
+    {
+        List<Node> evolved = new ArrayList<Node>(selectedCandidates.size());
+        for (Node node : selectedCandidates)
+        {
+            evolved.add(probability.nextEvent(rng) ? node.simplify() : node);
+        }
+        return evolved;
+    }
+}
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/geneticprogramming/Subtraction.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/geneticprogramming/Subtraction.java
new file mode 100644
index 0000000..97083af
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/geneticprogramming/Subtraction.java
@@ -0,0 +1,80 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.geneticprogramming;
+
+/**
+ * Simple subtraction operator {@link Node}.
+ * @author Daniel Dyer
+ */
+public class Subtraction extends BinaryNode
+{
+    /**
+     * Creates a node that evaluates the the value of {@literal left}
+     * minus the value of {@literal right}.
+     * @param left The first operand.
+     * @param right The second operand.
+     */
+    public Subtraction(Node left, Node right)
+    {
+        super(left, right, '-');
+    }
+
+
+    /**
+     * Evaluates the two sub-trees and returns the difference between these two values.
+     * @param programParameters Program parameters (ignored by the subtraction operator
+     * but may be used in evaluating the sub-trees).
+     * @return The difference between the values of the two child nodes.
+     */
+    public double evaluate(double[] programParameters)
+    {
+        return left.evaluate(programParameters) - right.evaluate(programParameters);
+    }
+
+
+    /**
+     * {@inheritDoc}
+     */
+    public Node simplify()
+    {
+        Node simplifiedLeft = left.simplify();
+        Node simplifiedRight = right.simplify();
+        // If the two arguments are identical then the result will always be zero.
+        if (simplifiedLeft.equals(simplifiedRight))
+        {
+            return new Constant(0);
+        }
+        // Subtracting zero is pointless, the expression can be reduced to its lefthand side.
+        else if (simplifiedRight instanceof Constant && simplifiedRight.evaluate(NO_ARGS) == 0)
+        {
+            return simplifiedLeft;
+        }
+        // If the two arguments are constants, we can simplify by calculating the result, it won't
+        // ever change.
+        else if (simplifiedLeft instanceof Constant && simplifiedRight instanceof Constant)
+        {
+            return new Constant(simplifiedLeft.evaluate(NO_ARGS) - simplifiedRight.evaluate(NO_ARGS));
+        }
+        else if (simplifiedLeft != left || simplifiedRight != right)
+        {
+            return new Subtraction(simplifiedLeft, simplifiedRight);
+        }
+        else
+        {
+            return this;
+        }
+    }
+}
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/geneticprogramming/SwingGPTreeRenderer.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/geneticprogramming/SwingGPTreeRenderer.java
new file mode 100644
index 0000000..fd16238
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/geneticprogramming/SwingGPTreeRenderer.java
@@ -0,0 +1,141 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.geneticprogramming;
+
+import java.awt.Color;
+import java.awt.Dimension;
+import java.awt.FontMetrics;
+import java.awt.Graphics;
+import java.awt.Graphics2D;
+import java.awt.RenderingHints;
+import javax.swing.JComponent;
+import org.uncommons.watchmaker.framework.interactive.Renderer;
+
+/**
+ * A Swing renderer for genetic programming trees.
+ * @author Daniel Dyer
+ */
+public class SwingGPTreeRenderer implements Renderer<Node, JComponent>
+{
+    /**
+     * Renders a GP tree as a Swing component.
+     * @param tree The root node of the GP tree to render.
+     * @return A {@link JComponent} that displays a graphical representation of the tree.
+     */
+    public JComponent render(Node tree)
+    {
+        return new GPTreeView(tree);
+    }
+
+
+    private static final class GPTreeView extends JComponent
+    {
+         // Allow 30 pixels for each node horizontally.
+        private static final int NODE_WIDTH = 30;
+         // Allow 50 pixels for each node vertically.
+        private static final int NODE_HEIGHT = 50;
+        private static final int CIRCLE_RADIUS = 9;
+        private static final int CIRCLE_DIAMETER = CIRCLE_RADIUS * 2;
+
+        private final Node rootNode;
+
+
+        GPTreeView(Node rootNode)
+        {
+            this.rootNode = rootNode;
+            int minHeight = rootNode.getDepth() * NODE_HEIGHT;
+            int minWidth = rootNode.getWidth() * NODE_WIDTH;
+            Dimension size = new Dimension(minWidth, minHeight);
+            setMinimumSize(size);
+            setPreferredSize(size);
+        }
+
+
+        @Override
+        protected void paintComponent(Graphics graphics)
+        {
+            super.paintComponent(graphics);
+            if (graphics instanceof Graphics2D)
+            {
+                ((Graphics2D) graphics).setRenderingHint(RenderingHints.KEY_ANTIALIASING,
+                                                         RenderingHints.VALUE_ANTIALIAS_ON);
+            }
+            // Center the tree if the component is bigger than required.
+            int offset = (getSize().width - getMinimumSize().width) / 2;
+            drawNode(rootNode, offset, 0, graphics);
+        }
+
+
+        /**
+         * Recursively draw the specified node and its children.
+         * @param node The sub-tree to draw.
+         * @param x The left edge of the area in which this tree is drawn.
+         * @param y The top edge of the area in which this tree is drawn.
+         * @param graphics The target for drawing.
+         */
+        private void drawNode(Node node, int x, int y, Graphics graphics)
+        {
+            int start = x + node.getWidth() * NODE_WIDTH / 2;
+            if (node instanceof Constant)
+            {
+                graphics.setColor(Color.YELLOW);
+                graphics.fillRoundRect(start - (NODE_WIDTH / 2 - 2),
+                                       y,
+                                       NODE_WIDTH - 4,
+                                       CIRCLE_DIAMETER,
+                                       CIRCLE_RADIUS,
+                                       CIRCLE_RADIUS);
+                graphics.setColor(Color.BLACK);
+                graphics.drawRoundRect(start - (NODE_WIDTH / 2 - 2),
+                                       y,
+                                       NODE_WIDTH - 4,
+                                       CIRCLE_DIAMETER,
+                                       CIRCLE_RADIUS,
+                                       CIRCLE_RADIUS);
+            }
+            else if (node instanceof Parameter)
+            {
+                graphics.setColor(Color.GREEN);
+                graphics.fillRect(start - CIRCLE_RADIUS, y, CIRCLE_DIAMETER, CIRCLE_DIAMETER);
+                graphics.setColor(Color.BLACK);
+                graphics.drawRect(start - CIRCLE_RADIUS, y, CIRCLE_DIAMETER, CIRCLE_DIAMETER);
+            }
+            else
+            {
+                graphics.setColor(Color.WHITE);
+                graphics.fillOval(start - CIRCLE_RADIUS, y, CIRCLE_DIAMETER, CIRCLE_DIAMETER);
+                graphics.setColor(Color.BLACK);
+                graphics.drawOval(start - CIRCLE_RADIUS, y, CIRCLE_DIAMETER, CIRCLE_DIAMETER);
+            }
+            FontMetrics metrics = graphics.getFontMetrics();
+            int stringWidth = metrics.stringWidth(node.getLabel());
+            graphics.drawString(node.getLabel(),
+                                (int) Math.round(start - (double) stringWidth / 2),
+                                (int) Math.round(y + CIRCLE_RADIUS + (double) metrics.getHeight() / 2 - metrics.getDescent()));
+
+            int xOffset = x;
+            for (int i = 0; i < node.getArity(); i++)
+            {
+                Node child = node.getChild(i);
+                drawNode(child, xOffset, y + NODE_HEIGHT, graphics);
+                graphics.drawLine(start,
+                                  y + CIRCLE_DIAMETER, xOffset + (child.getWidth() * NODE_WIDTH / 2),
+                                  y + NODE_HEIGHT);
+                xOffset += child.getWidth() * NODE_WIDTH;
+            }
+        }
+    }
+}
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/geneticprogramming/TreeCrossover.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/geneticprogramming/TreeCrossover.java
new file mode 100644
index 0000000..8fe711e
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/geneticprogramming/TreeCrossover.java
@@ -0,0 +1,72 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.geneticprogramming;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Random;
+import org.uncommons.watchmaker.framework.operators.AbstractCrossover;
+
+/**
+ * Cross-over operator for the trees of {@link Node}s used in the genetic
+ * programming example application.
+ * @author Daniel Dyer
+ */
+public class TreeCrossover extends AbstractCrossover<Node>
+{
+    /**
+     * Creates a single-point cross-over operator.
+     */
+    public TreeCrossover()
+    {
+        super(1);
+    }
+
+
+    /**
+     * Swaps randomly selected sub-trees between the two parents.
+     * @param parent1 The first parent.
+     * @param parent2 The second parent.
+     * @param numberOfCrossoverPoints The number of cross-overs to perform.
+     * @param rng A source of randomness.
+     * @return A list of two offspring, generated by swapping sub-trees
+     * between the two parents.
+     */
+    @Override
+    protected List<Node> mate(Node parent1,
+                              Node parent2,
+                              int numberOfCrossoverPoints,
+                              Random rng)
+    {
+        List<Node> offspring = new ArrayList<Node>(2);
+        Node offspring1 = parent1;
+        Node offspring2 = parent2;
+
+        for (int i = 0; i < numberOfCrossoverPoints; i++)
+        {
+            int crossoverPoint1 = rng.nextInt(parent1.countNodes());
+            Node subTree1 = parent1.getNode(crossoverPoint1);
+            int crossoverPoint2 = rng.nextInt(parent2.countNodes());
+            Node subTree2 = parent2.getNode(crossoverPoint2);
+            offspring1 = parent1.replaceNode(crossoverPoint1, subTree2);
+            offspring2 = parent2.replaceNode(crossoverPoint2, subTree1);
+        }
+
+        offspring.add(offspring1);
+        offspring.add(offspring2);
+        return offspring;
+    }
+}
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/geneticprogramming/TreeEvaluator.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/geneticprogramming/TreeEvaluator.java
new file mode 100644
index 0000000..57e718b
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/geneticprogramming/TreeEvaluator.java
@@ -0,0 +1,79 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.geneticprogramming;
+
+import java.util.List;
+import java.util.Map;
+import org.uncommons.watchmaker.framework.FitnessEvaluator;
+
+/**
+ * Fitness function for the genetic programming example application.
+ * An evolved program tree is tested against a table of inputs and associated
+ * expected outputs.  If the evolved program correctly calculates the right answer
+ * for all sets of inputs then it has a fitness of zero.  Otherwise, its fitness
+ * is an error value that indicates how accurate it was (the larger the combined
+ * error value, the less accurate the function is). 
+ * @author Daniel Dyer
+ */
+public class TreeEvaluator implements FitnessEvaluator<Node>
+{
+    private final Map<double[], Double> data;
+
+
+    /**
+     * @param data Each row is consists of a set of inputs and an expected output (the
+     * last item in the row is the output).
+     */
+    public TreeEvaluator(Map<double[], Double> data)
+    {
+        this.data = data;
+    }
+
+
+    /**
+     * If the evolved program correctly calculates the right answer
+     * for all sets of inputs then it has a fitness of zero.  Otherwise, its fitness
+     * is an error value that indicates how accurate it was (the larger the combined
+     * error value, the less accurate the function is).
+     * The combined error value is calculated by summing the squares of each individual
+     * error (the difference between the expected output and the actual output).
+     * @param candidate The program tree to evaluate.
+     * @param population Ignored by this implementation.
+     * @return The fitness score for the specified candidate.
+     */
+    public double getFitness(Node candidate, List<? extends Node> population)
+    {
+        double error = 0;
+        for (Map.Entry<double[], Double> entry : data.entrySet())
+        {
+            double actualValue = candidate.evaluate(entry.getKey());
+            double diff = actualValue - entry.getValue();
+            error += (diff * diff);
+        }
+        return error;
+    }
+
+
+    /**
+     * This fitness evaluator is a minimising function.  A fitness of zero
+     * indicates a perfect solution.
+     * @return false
+     */
+    public boolean isNatural()
+    {
+        return false;
+    }
+}
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/geneticprogramming/TreeFactory.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/geneticprogramming/TreeFactory.java
new file mode 100644
index 0000000..abb935d
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/geneticprogramming/TreeFactory.java
@@ -0,0 +1,115 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.geneticprogramming;
+
+import java.util.Random;
+import org.uncommons.maths.random.Probability;
+import org.uncommons.watchmaker.framework.factories.AbstractCandidateFactory;
+
+/**
+ * {@link org.uncommons.watchmaker.framework.CandidateFactory} for generating
+ * trees of {@link Node}s for the genetic programming example application.
+ * @author Daniel Dyer
+ */
+public class TreeFactory extends AbstractCandidateFactory<Node>
+{
+    // The number of program parameters that each program tree will be provided.
+    private final int parameterCount;
+
+    // The maximum depth of a program tree.  No function nodes will be created below
+    // this depth (branches will be terminated with parameters or constants).
+    private final int maximumDepth;
+
+    // Probability that a created node is a function node rather
+    // than a value node.
+    private final Probability functionProbability;
+
+    // Probability that a value (non-function) node is a parameter
+    // node rather than a constant node.
+    private final Probability parameterProbability;
+
+
+    /**
+     * @param parameterCount The number of program parameters that each
+     * generated program tree can will be provided when executed.
+     * @param maxDepth The maximum depth of generated trees.
+     * @param functionProbability The probability (between 0 and 1) that a
+     * randomly-generated node will be a function node rather than a value
+     * (parameter or constant) node.
+     * @param parameterProbability The probability that a randomly-generated
+     * non-function node will be a parameter node rather than a constant node.
+     */
+    public TreeFactory(int parameterCount,
+                       int maxDepth,
+                       Probability functionProbability,
+                       Probability parameterProbability)
+    {
+        if (parameterCount < 0)
+        {
+            throw new IllegalArgumentException("Parameter count must be greater than or equal to 0.");
+        }
+        if (maxDepth < 1)
+        {
+            throw new IllegalArgumentException("Max depth must be at least 1.");
+        }
+
+        this.parameterCount = parameterCount;
+        this.maximumDepth = maxDepth;
+        this.functionProbability = functionProbability;
+        this.parameterProbability = parameterProbability;
+    }
+
+
+    /**
+     * {@inheritDoc}
+     */
+    public Node generateRandomCandidate(Random rng)
+    {
+        return makeNode(rng, maximumDepth);
+    }
+
+
+    /**
+     * Recursively constructs a tree of Nodes, up to the specified maximum depth.
+     * @param rng The RNG used to random create nodes.
+     * @param maxDepth The maximum depth of the generated tree.
+     * @return A tree of nodes.
+     */
+    private Node makeNode(Random rng, int maxDepth)
+    {
+        if (functionProbability.nextEvent(rng) && maxDepth > 1)
+        {
+            // Max depth for sub-trees is one less than max depth for this node.
+            int depth = maxDepth - 1;
+            switch (rng.nextInt(5))
+            {
+                case 0: return new Addition(makeNode(rng, depth), makeNode(rng, depth));
+                case 1: return new Subtraction(makeNode(rng, depth), makeNode(rng, depth));
+                case 2: return new Multiplication(makeNode(rng, depth), makeNode(rng, depth));
+                case 3: return new IfThenElse(makeNode(rng, depth), makeNode(rng, depth), makeNode(rng, depth));
+                default: return new IsGreater(makeNode(rng, depth), makeNode(rng, depth));
+            }
+        }
+        else if (parameterProbability.nextEvent(rng))
+        {
+            return new Parameter(rng.nextInt(parameterCount));
+        }
+        else
+        {
+            return new Constant(rng.nextInt(11));
+        }
+    }
+}
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/geneticprogramming/TreeMutation.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/geneticprogramming/TreeMutation.java
new file mode 100644
index 0000000..75f64b5
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/geneticprogramming/TreeMutation.java
@@ -0,0 +1,61 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.geneticprogramming;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Random;
+import org.uncommons.maths.random.Probability;
+import org.uncommons.watchmaker.framework.EvolutionaryOperator;
+
+/**
+ * Mutation operator for the trees of {@link Node}s used in the genetic
+ * programming example application.
+ * @author Daniel Dyer
+ */
+public class TreeMutation implements EvolutionaryOperator<Node>
+{
+    private final TreeFactory treeFactory;
+
+    private final Probability mutationProbability;
+
+    /**
+     * The tree mutation operator requires a {@link TreeFactory} because
+     * the process of mutation involves creating new sub-trees.  The same
+     * TreeFactory that is used to create the initial population should be
+     * used.
+     * @param treeFactory Used to generate the new sub-trees required for mutation.
+     * @param mutationProbability The probability that any given node in a tree is
+     * mutated by this operator.
+     */
+    public TreeMutation(TreeFactory treeFactory,
+                        Probability mutationProbability)
+    {
+        this.treeFactory = treeFactory;
+        this.mutationProbability = mutationProbability;
+    }
+
+
+    public List<Node> apply(List<Node> selectedCandidates, Random rng)
+    {
+        List<Node> mutatedPopulation = new ArrayList<Node>(selectedCandidates.size());
+        for (Node tree : selectedCandidates)
+        {
+            mutatedPopulation.add(tree.mutate(rng, mutationProbability, treeFactory));
+        }
+        return mutatedPopulation;
+    }
+}
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/geneticprogramming/package-info.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/geneticprogramming/package-info.java
new file mode 100644
index 0000000..2aa8b11
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/geneticprogramming/package-info.java
@@ -0,0 +1,20 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+/**
+ * A simple example of tree-based genetic programming.
+ * @author Daniel Dyer
+ */
+package org.uncommons.watchmaker.examples.geneticprogramming;
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/monalisa/AbstractVertexMutation.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/monalisa/AbstractVertexMutation.java
new file mode 100644
index 0000000..490ed92
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/monalisa/AbstractVertexMutation.java
@@ -0,0 +1,101 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.monalisa;
+
+import java.awt.Dimension;
+import java.awt.Point;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Random;
+import org.uncommons.maths.number.NumberGenerator;
+import org.uncommons.maths.random.Probability;
+import org.uncommons.watchmaker.framework.EvolutionaryOperator;
+
+/**
+ * Base class for mutation operators that modify the points of polygons in an
+ * image.
+ * @author Daniel Dyer
+ */
+abstract class AbstractVertexMutation implements EvolutionaryOperator<ColouredPolygon>
+{
+    private final Dimension canvasSize;
+    private final NumberGenerator<Probability> mutationProbability;
+
+
+    /**
+     * @param mutationProbability A {@link NumberGenerator} that controls the probability
+     * that a polygon's points will be mutated.
+     * @param canvasSize The size of the canvas.  Used to constrain the positions of the points.
+     */
+    protected AbstractVertexMutation(NumberGenerator<Probability> mutationProbability,
+                                     Dimension canvasSize)
+    {
+        this.mutationProbability = mutationProbability;
+        this.canvasSize = canvasSize;
+    }
+
+
+    /**
+     * @return The dimensions of the target image.
+     */
+    protected Dimension getCanvasSize()
+    {
+        return canvasSize;
+    }
+
+
+    /**
+     * @return The {@link NumberGenerator} that provides the mutation probability.
+     */
+    protected NumberGenerator<Probability> getMutationProbability()
+    {
+        return mutationProbability;
+    }
+
+
+    /**
+     * Applies the mutation to each polygon in the list provided according to the
+     * pre-configured mutation probability.  If the probability is 0.1, approximately
+     * 10% of the individuals will be mutated.  The actual mutation operation is
+     * defined in the sub-class implementation of the
+     * {@link #mutateVertices(java.util.List, java.util.Random)} method.
+     * @param polygons The list of polygons to be mutated.
+     * @param rng A source of randomness.
+     * @return The polygons after mutation.  None, some or all will have been
+     * modified. 
+     */
+    public List<ColouredPolygon> apply(List<ColouredPolygon> polygons, Random rng)
+    {
+        List<ColouredPolygon> newPolygons = new ArrayList<ColouredPolygon>(polygons.size());
+        for (ColouredPolygon polygon : polygons)
+        {
+            List<Point> newVertices = mutateVertices(polygon.getVertices(), rng);
+            newPolygons.add(newVertices == polygon.getVertices()
+                            ? polygon
+                            : new ColouredPolygon(polygon.getColour(), newVertices));
+        }
+        return newPolygons;
+    }
+
+
+    /**
+     * Implemented in sub-classes to perform the mutation of the vertices.
+     * @param vertices A list of the points that make up the polygon.
+     * @param rng A source of randomness.
+     * @return A mutated list of points.
+     */
+    protected abstract List<Point> mutateVertices(List<Point> vertices, Random rng);
+}
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/monalisa/AddPolygonMutation.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/monalisa/AddPolygonMutation.java
new file mode 100644
index 0000000..183a8b7
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/monalisa/AddPolygonMutation.java
@@ -0,0 +1,97 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.monalisa;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Random;
+import org.uncommons.maths.number.ConstantGenerator;
+import org.uncommons.maths.number.NumberGenerator;
+import org.uncommons.maths.random.Probability;
+import org.uncommons.watchmaker.framework.EvolutionaryOperator;
+
+/**
+ * Randomly mutates the polygons that make up an image by adding a polygon
+ * according to some probability.
+ * @author Daniel Dyer
+ */
+public class AddPolygonMutation implements EvolutionaryOperator<List<ColouredPolygon>>
+{
+    private final NumberGenerator<Probability> addPolygonProbability;
+    private final PolygonImageFactory factory;
+    private final int maxPolygons;
+
+
+
+    /**
+     * @param addPolygonProbability A {@link NumberGenerator} that controls the probability
+     * that a polygon will be added.
+     * @param factory Used to create new polygons.
+     * @param maxPolygons The maximum number of polygons permitted in an image (must be at least 2).
+     */
+    public AddPolygonMutation(NumberGenerator<Probability> addPolygonProbability,
+                              PolygonImageFactory factory,
+                              int maxPolygons)
+    {
+        if (maxPolygons < 2)
+        {
+            throw new IllegalArgumentException("Max polygons must be > 1.");
+        }
+        this.addPolygonProbability = addPolygonProbability;
+        this.factory = factory;
+        this.maxPolygons = maxPolygons;
+    }
+
+
+    /**
+     * @param addPolygonProbability The probability that a polygon will be removed.
+     * @param factory Used to create new polygons.
+     * @param maxPolygons The maximum number of polygons permitted in an image (must be at least 2).
+     */
+    public AddPolygonMutation(Probability addPolygonProbability,
+                              PolygonImageFactory factory,
+                              int maxPolygons)
+    {
+        this(new ConstantGenerator<Probability>(addPolygonProbability),
+             factory,
+             maxPolygons);
+    }
+
+
+    public List<List<ColouredPolygon>> apply(List<List<ColouredPolygon>> selectedCandidates, Random rng)
+    {
+        List<List<ColouredPolygon>> mutatedCandidates = new ArrayList<List<ColouredPolygon>>(selectedCandidates.size());
+        for (List<ColouredPolygon> candidate : selectedCandidates)
+        {
+            // A single polygon is added with the configured probability, unless
+            // we already have the maximum permitted number of polygons.
+            if (candidate.size() < maxPolygons && addPolygonProbability.nextValue().nextEvent(rng))
+            {
+                List<ColouredPolygon> newPolygons = new ArrayList<ColouredPolygon>(candidate);
+                newPolygons.add(rng.nextInt(newPolygons.size() + 1),
+                                factory.createRandomPolygon(rng));
+                mutatedCandidates.add(newPolygons);
+            }
+            else // Nothing changed.
+            {
+                mutatedCandidates.add(candidate);
+            }
+        }
+        return mutatedCandidates;
+    }
+
+
+}
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/monalisa/AddVertexMutation.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/monalisa/AddVertexMutation.java
new file mode 100644
index 0000000..decebdd
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/monalisa/AddVertexMutation.java
@@ -0,0 +1,84 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.monalisa;
+
+import java.awt.Dimension;
+import java.awt.Point;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Random;
+import org.uncommons.maths.number.ConstantGenerator;
+import org.uncommons.maths.number.NumberGenerator;
+import org.uncommons.maths.random.Probability;
+
+/**
+ * Evolutionary operator for mutating individual polygons.  Polygons are mutated
+ * by adding a point, according to some probability.
+ * @author Daniel Dyer
+ */
+public class AddVertexMutation extends AbstractVertexMutation
+{
+    static final int MAX_VERTEX_COUNT = 10;
+
+    /**
+     * @param mutationProbability A {@link NumberGenerator} that controls the probability
+     * that a point will be added.
+     * @param canvasSize The size of the canvas.  Used to constrain the positions of the points.
+     */
+    public AddVertexMutation(Dimension canvasSize,
+                             NumberGenerator<Probability> mutationProbability)
+    {
+        super(mutationProbability, canvasSize);
+    }
+
+
+    /**
+     * @param mutationProbability The probability that a point will be added.
+     * @param canvasSize The size of the canvas.  Used to constrain the positions of the points.
+     */
+    public AddVertexMutation(Dimension canvasSize,
+                             Probability mutationProbability)
+    {
+        this(canvasSize, new ConstantGenerator<Probability>(mutationProbability));
+    }
+
+
+    /**
+     * Mutates the list of vertices for a given polygon by adding a new random point.
+     * Whether or not a point is actually added is determined by the configured mutation probability.
+     * @param vertices A list of the points that make up the polygon.
+     * @param rng A source of randomness.
+     * @return A mutated list of points.
+     */
+    @Override
+    protected List<Point> mutateVertices(List<Point> vertices, Random rng)
+    {
+        // A single point is added with the configured probability, unless
+        // we already have the maximum permitted number of points.
+        if (vertices.size() < MAX_VERTEX_COUNT && getMutationProbability().nextValue().nextEvent(rng))
+        {
+            List<Point> newVertices = new ArrayList<Point>(vertices);
+            newVertices.add(rng.nextInt(newVertices.size()),
+                            new Point(rng.nextInt(getCanvasSize().width),
+                                      rng.nextInt(getCanvasSize().height)));
+            return newVertices;
+        }
+        else // Nothing changed.
+        {
+            return vertices;
+        }
+    }
+}
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/monalisa/AdjustVertexMutation.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/monalisa/AdjustVertexMutation.java
new file mode 100644
index 0000000..0549cc6
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/monalisa/AdjustVertexMutation.java
@@ -0,0 +1,94 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.monalisa;
+
+import java.awt.Dimension;
+import java.awt.Point;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Random;
+import org.uncommons.maths.Maths;
+import org.uncommons.maths.number.ConstantGenerator;
+import org.uncommons.maths.number.NumberGenerator;
+import org.uncommons.maths.random.Probability;
+
+/**
+ * Evolutionary operator for mutating individual polygons.  Polygons are mutated
+ * by moving a point, according to some probability.
+ * @author Daniel Dyer
+ */
+public class AdjustVertexMutation extends AbstractVertexMutation
+{
+    private final NumberGenerator<? extends Number> changeAmount;
+
+    /**
+     * @param mutationProbability A {@link NumberGenerator} that controls the
+     * probability that a point will be moved.
+     * @param canvasSize The size of the canvas.  Used to constrain the positions
+     * of the points.
+     * @param changeAmount A {@link NumberGenerator} that controls the distance
+     * that points are moved (in pixels).  Should generate both positive and
+     * negative values.
+     */
+    public AdjustVertexMutation(Dimension canvasSize,
+                                NumberGenerator<Probability> mutationProbability,
+                                NumberGenerator<? extends Number> changeAmount)
+    {
+        super(mutationProbability, canvasSize);
+        this.changeAmount = changeAmount;
+    }
+
+
+    /**
+     * @param mutationProbability The probability that a point will be moved.
+     * @param canvasSize The size of the canvas.  Used to constrain the positions
+     * of the points.
+     * @param changeAmount A {@link NumberGenerator} that controls the distance
+     * that points are moved (in pixels).  Should generate both positive and
+     * negative values.
+     */
+    public AdjustVertexMutation(Dimension canvasSize,
+                                Probability mutationProbability,
+                                NumberGenerator<? extends Number> changeAmount)
+    {
+        this(canvasSize, new ConstantGenerator<Probability>(mutationProbability), changeAmount);
+    }
+
+
+    @Override
+    protected List<Point> mutateVertices(List<Point> vertices, Random rng)
+    {
+        // A single point is modified with the configured probability.
+        if (getMutationProbability().nextValue().nextEvent(rng))
+        {
+            List<Point> newVertices = new ArrayList<Point>(vertices);
+            int xDelta = (int) Math.round(changeAmount.nextValue().doubleValue());
+            int yDelta = (int) Math.round(changeAmount.nextValue().doubleValue());
+            int index = rng.nextInt(newVertices.size());
+            Point oldPoint = newVertices.get(index);
+            int newX = oldPoint.x + xDelta;
+            int newY = oldPoint.y + yDelta;
+            newX = Maths.restrictRange(newX, 0, getCanvasSize().width - 1);
+            newY = Maths.restrictRange(newY, 0, getCanvasSize().height - 1);
+            newVertices.set(index, new Point(newX, newY));
+            return newVertices;
+        }
+        else // Nothing changed.
+        {
+            return vertices;
+        }
+    }
+}
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/monalisa/ColouredPolygon.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/monalisa/ColouredPolygon.java
new file mode 100644
index 0000000..eb8c481
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/monalisa/ColouredPolygon.java
@@ -0,0 +1,78 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.monalisa;
+
+import java.awt.Color;
+import java.awt.Point;
+import java.awt.Polygon;
+import java.util.List;
+
+/**
+ * A coloured polygon consists of a set of vertices and a colour that is used to
+ * fill the polygon when it is rendered.
+ * @author Daniel Dyer
+ */
+public class ColouredPolygon
+{
+    private final Color colour;
+    private final List<Point> vertices;
+    private final Polygon polygon;
+
+
+    /**
+     * Creates a new filled polygon with the specified points and colour.
+     * @param colour The colour of this polygon.  The alpha channel is used
+     * to specify the polygons translucency.
+     * @param vertices The points that define the polygon's outline.
+     */
+    public ColouredPolygon(Color colour, List<Point> vertices)
+    {
+        this.colour = colour;
+        this.vertices = vertices;
+        this.polygon = new Polygon();
+        for (Point point : vertices)
+        {
+            polygon.addPoint(point.x, point.y);
+        }
+    }
+
+
+    /**
+     * @return The colour that this polygon should be rendered.
+     */
+    public Color getColour()
+    {
+        return colour;
+    }
+
+
+    /**
+     * @return A list of this polygon's vertices.
+     */
+    public List<Point> getVertices()
+    {
+        return vertices;
+    }
+
+
+    /**
+     * @return The AWT shape used for rendering.
+     */
+    public Polygon getPolygon()
+    {
+        return polygon;
+    }
+}
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/monalisa/MonaLisaApplet.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/monalisa/MonaLisaApplet.java
new file mode 100644
index 0000000..4a0db99
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/monalisa/MonaLisaApplet.java
@@ -0,0 +1,249 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.monalisa;
+
+import java.awt.BorderLayout;
+import java.awt.Container;
+import java.awt.Dimension;
+import java.awt.event.ActionEvent;
+import java.awt.event.ActionListener;
+import java.awt.image.BufferedImage;
+import java.io.IOException;
+import java.net.URL;
+import java.util.List;
+import java.util.Random;
+import javax.imageio.ImageIO;
+import javax.swing.BorderFactory;
+import javax.swing.Box;
+import javax.swing.JButton;
+import javax.swing.JComponent;
+import javax.swing.JLabel;
+import javax.swing.JOptionPane;
+import javax.swing.JPanel;
+import javax.swing.JSpinner;
+import javax.swing.SpinnerNumberModel;
+import org.uncommons.maths.random.Probability;
+import org.uncommons.maths.random.XORShiftRNG;
+import org.uncommons.swing.SwingBackgroundTask;
+import org.uncommons.watchmaker.examples.AbstractExampleApplet;
+import org.uncommons.watchmaker.framework.CachingFitnessEvaluator;
+import org.uncommons.watchmaker.framework.EvolutionEngine;
+import org.uncommons.watchmaker.framework.EvolutionaryOperator;
+import org.uncommons.watchmaker.framework.FitnessEvaluator;
+import org.uncommons.watchmaker.framework.GenerationalEvolutionEngine;
+import org.uncommons.watchmaker.framework.SelectionStrategy;
+import org.uncommons.watchmaker.framework.TerminationCondition;
+import org.uncommons.watchmaker.framework.interactive.Renderer;
+import org.uncommons.watchmaker.framework.selection.TournamentSelection;
+import org.uncommons.watchmaker.framework.termination.Stagnation;
+import org.uncommons.watchmaker.swing.AbortControl;
+import org.uncommons.watchmaker.swing.ProbabilityParameterControl;
+import org.uncommons.watchmaker.swing.evolutionmonitor.EvolutionMonitor;
+
+/**
+ * This program is inspired by Roger Alsing's evolution of the Mona Lisa
+ * (http://rogeralsing.com/2008/12/07/genetic-programming-evolution-of-mona-lisa/).
+ * It attempts to find the combination of 50 translucent polygons that most closely
+ * resembles Leonardo da Vinci's Mona Lisa.
+ * @author Daniel Dyer
+ */
+public class MonaLisaApplet extends AbstractExampleApplet
+{
+    private static final String IMAGE_PATH = "org/uncommons/watchmaker/examples/monalisa/monalisa.jpg";
+
+    private ProbabilitiesPanel probabilitiesPanel;
+    private EvolutionMonitor<List<ColouredPolygon>> monitor;
+    private JButton startButton;
+    private AbortControl abort;
+    private JSpinner populationSpinner;
+    private JSpinner elitismSpinner;
+    private ProbabilityParameterControl selectionPressureControl;
+    private BufferedImage targetImage;
+
+
+    @Override
+    public void init()
+    {
+        try
+        {
+            URL imageURL = MonaLisaApplet.class.getClassLoader().getResource(IMAGE_PATH);
+            targetImage = ImageIO.read(imageURL);
+            super.init();
+        }
+        catch (IOException ex)
+        {
+            ex.printStackTrace();
+            JOptionPane.showMessageDialog(this, ex, "Failed to Load Image", JOptionPane.ERROR_MESSAGE);
+
+        }
+    }
+
+
+    /**
+     * Initialise and layout the GUI.
+     * @param container The Swing component that will contain the GUI controls.
+     */
+    @Override
+    protected void prepareGUI(Container container)
+    {
+        probabilitiesPanel = new ProbabilitiesPanel();
+        probabilitiesPanel.setBorder(BorderFactory.createTitledBorder("Evolution Probabilities"));        
+        JPanel controls = new JPanel(new BorderLayout());
+        controls.add(createParametersPanel(), BorderLayout.NORTH);
+        controls.add(probabilitiesPanel, BorderLayout.SOUTH);
+        container.add(controls, BorderLayout.NORTH);
+
+        Renderer<List<ColouredPolygon>, JComponent> renderer = new PolygonImageSwingRenderer(targetImage);
+        monitor = new EvolutionMonitor<List<ColouredPolygon>>(renderer, false);
+        container.add(monitor.getGUIComponent(), BorderLayout.CENTER);
+    }
+
+
+    private JComponent createParametersPanel()
+    {
+        Box parameters = Box.createHorizontalBox();
+        parameters.add(Box.createHorizontalStrut(10));
+        final JLabel populationLabel = new JLabel("Population Size: ");
+        parameters.add(populationLabel);
+        parameters.add(Box.createHorizontalStrut(10));
+        populationSpinner = new JSpinner(new SpinnerNumberModel(10, 2, 1000, 1));
+        populationSpinner.setMaximumSize(populationSpinner.getMinimumSize());
+        parameters.add(populationSpinner);
+        parameters.add(Box.createHorizontalStrut(10));
+        final JLabel elitismLabel = new JLabel("Elitism: ");
+        parameters.add(elitismLabel);
+        parameters.add(Box.createHorizontalStrut(10));
+        elitismSpinner = new JSpinner(new SpinnerNumberModel(2, 1, 1000, 1));
+        elitismSpinner.setMaximumSize(elitismSpinner.getMinimumSize());
+        parameters.add(elitismSpinner);
+        parameters.add(Box.createHorizontalStrut(10));
+
+        parameters.add(new JLabel("Selection Pressure: "));
+        parameters.add(Box.createHorizontalStrut(10));
+        selectionPressureControl = new ProbabilityParameterControl(Probability.EVENS,
+                                                                   Probability.ONE,
+                                                                   2,
+                                                                   new Probability(0.7));
+        parameters.add(selectionPressureControl.getControl());
+        parameters.add(Box.createHorizontalStrut(10));
+
+        startButton = new JButton("Start");
+        abort = new AbortControl();        
+        startButton.addActionListener(new ActionListener()
+        {
+            public void actionPerformed(ActionEvent ev)
+            {
+                abort.getControl().setEnabled(true);
+                populationLabel.setEnabled(false);
+                populationSpinner.setEnabled(false);
+                elitismLabel.setEnabled(false);
+                elitismSpinner.setEnabled(false);
+                startButton.setEnabled(false);
+                new EvolutionTask((Integer) populationSpinner.getValue(),
+                                  (Integer) elitismSpinner.getValue(),
+                                  abort.getTerminationCondition(),
+                                  new Stagnation(1000, false)).execute();
+            }
+        });
+        abort.getControl().setEnabled(false);
+        parameters.add(startButton);
+        parameters.add(abort.getControl());
+        parameters.add(Box.createHorizontalStrut(10));
+
+        parameters.setBorder(BorderFactory.createTitledBorder("Parameters"));
+        return parameters;
+    }
+
+
+    /**
+     * Entry point for running this example as an application rather than an applet.
+     * @param args Program arguments (ignored).
+     * @throws IOException If there is a problem loading the target image. 
+     */
+    public static void main(String[] args) throws IOException
+    {
+        MonaLisaApplet gui = new MonaLisaApplet();
+        // If a URL is specified as an argument, use that image.  Otherwise use the default Mona Lisa picture.
+        URL imageURL = args.length > 0
+                       ? new URL(args[0])
+                       : MonaLisaApplet.class.getClassLoader().getResource(IMAGE_PATH);
+        gui.targetImage = ImageIO.read(imageURL);
+        gui.displayInFrame("Watchmaker Framework - Mona Lisa Example");
+    }
+
+
+    /**
+     * The task that acutally performs the evolution.
+     */
+    private class EvolutionTask extends SwingBackgroundTask<List<ColouredPolygon>>
+    {
+        private final int populationSize;
+        private final int eliteCount;
+        private final TerminationCondition[] terminationConditions;
+
+
+        EvolutionTask(int populationSize, int eliteCount, TerminationCondition... terminationConditions)
+        {
+            this.populationSize = populationSize;
+            this.eliteCount = eliteCount;
+            this.terminationConditions = terminationConditions;
+        }
+
+
+        @Override
+        protected List<ColouredPolygon> performTask() throws Exception
+        {
+            Dimension canvasSize = new Dimension(targetImage.getWidth(), targetImage.getHeight());
+
+            Random rng = new XORShiftRNG();
+            FitnessEvaluator<List<ColouredPolygon>> evaluator
+                = new CachingFitnessEvaluator<List<ColouredPolygon>>(new PolygonImageEvaluator(targetImage));
+            PolygonImageFactory factory = new PolygonImageFactory(canvasSize);
+            EvolutionaryOperator<List<ColouredPolygon>> pipeline
+                = probabilitiesPanel.createEvolutionPipeline(factory, canvasSize, rng);
+
+            SelectionStrategy<Object> selection = new TournamentSelection(selectionPressureControl.getNumberGenerator());
+            EvolutionEngine<List<ColouredPolygon>> engine
+                = new GenerationalEvolutionEngine<List<ColouredPolygon>>(factory,
+                                                                         pipeline,
+                                                                         evaluator,
+                                                                         selection,
+                                                                         rng);
+            engine.addEvolutionObserver(monitor);
+
+            return engine.evolve(populationSize, eliteCount, terminationConditions);
+        }
+
+
+        @Override
+        protected void postProcessing(List<ColouredPolygon> result)
+        {
+            abort.reset();
+            abort.getControl().setEnabled(false);
+            populationSpinner.setEnabled(true);
+            elitismSpinner.setEnabled(true);
+            startButton.setEnabled(true);
+        }
+
+
+        @Override
+        protected void onError(Throwable throwable)
+        {
+            super.onError(throwable);
+            postProcessing(null);
+        }
+    }
+}
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/monalisa/MovePolygonMutation.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/monalisa/MovePolygonMutation.java
new file mode 100644
index 0000000..1b91f73
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/monalisa/MovePolygonMutation.java
@@ -0,0 +1,74 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.monalisa;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Random;
+import org.uncommons.maths.number.ConstantGenerator;
+import org.uncommons.maths.number.NumberGenerator;
+import org.uncommons.maths.random.Probability;
+import org.uncommons.watchmaker.framework.EvolutionaryOperator;
+
+/**
+ * Randomly mutates an image by swapping the z-order of two of its polygons
+ * according to some probability.
+ * @author Daniel Dyer
+ */
+public class MovePolygonMutation implements EvolutionaryOperator<List<ColouredPolygon>>
+{
+    private final NumberGenerator<Probability> movePolygonProbability;
+
+
+    /**
+     * @param movePolygonProbability A {@link NumberGenerator} that controls the probability
+     * that a polygon will be replaced.
+     */
+    public MovePolygonMutation(NumberGenerator<Probability> movePolygonProbability)
+    {
+        this.movePolygonProbability = movePolygonProbability;
+    }
+
+
+    /**
+     * @param replacePolygonProbability The probability that a polygon will be replaced.
+     */
+    public MovePolygonMutation(Probability replacePolygonProbability)
+    {
+        this(new ConstantGenerator<Probability>(replacePolygonProbability));
+    }
+
+
+    public List<List<ColouredPolygon>> apply(List<List<ColouredPolygon>> selectedCandidates, Random rng)
+    {
+        List<List<ColouredPolygon>> mutatedCandidates = new ArrayList<List<ColouredPolygon>>(selectedCandidates.size());
+        for (List<ColouredPolygon> candidate : selectedCandidates)
+        {
+            if (movePolygonProbability.nextValue().nextEvent(rng))
+            {
+                List<ColouredPolygon> newPolygons = new ArrayList<ColouredPolygon>(candidate);
+                ColouredPolygon polygon = newPolygons.remove(rng.nextInt(newPolygons.size()));
+                newPolygons.add(rng.nextInt(newPolygons.size()) + 1, polygon);
+                mutatedCandidates.add(newPolygons);
+            }
+            else // Nothing changed.
+            {
+                mutatedCandidates.add(candidate);
+            }
+        }
+        return mutatedCandidates;
+    }
+}
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/monalisa/PolygonColourMutation.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/monalisa/PolygonColourMutation.java
new file mode 100644
index 0000000..0434646
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/monalisa/PolygonColourMutation.java
@@ -0,0 +1,113 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.monalisa;
+
+import java.awt.Color;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Random;
+import org.uncommons.maths.Maths;
+import org.uncommons.maths.number.ConstantGenerator;
+import org.uncommons.maths.number.NumberGenerator;
+import org.uncommons.maths.random.Probability;
+import org.uncommons.watchmaker.framework.EvolutionaryOperator;
+
+/**
+ * Evolutionary operator for mutating individual polygons.  Polygons are mutated
+ * by changing their colour and/or either adding a point, removing a point or
+ * changing the position of a point.
+ * @author Daniel Dyer
+ */
+public class PolygonColourMutation implements EvolutionaryOperator<ColouredPolygon>
+{
+    private final NumberGenerator<Probability> mutationProbability;
+    private final NumberGenerator<Double> mutationAmount;
+
+
+    /**
+     * @param mutationProbability A {@link NumberGenerator} that controls the
+     * probability that the colour will be modified.
+     * @param mutationAmount A {@link NumberGenerator} that controls the amount
+     * that the colour's components are adjusted by.
+     */
+    public PolygonColourMutation(NumberGenerator<Probability> mutationProbability,
+                                 NumberGenerator<Double> mutationAmount)
+    {
+        this.mutationProbability = mutationProbability;
+        this.mutationAmount = mutationAmount;
+    }
+
+
+    /**
+     * @param mutationProbability The probability that the colour will be modified.
+     * @param mutationAmount A {@link NumberGenerator} that controls the amount
+     * that the colour's components are adjusted by.
+     */
+    public PolygonColourMutation(Probability mutationProbability,
+                                 NumberGenerator<Double> mutationAmount)
+    {
+        this(new ConstantGenerator<Probability>(mutationProbability), mutationAmount);
+    }
+
+
+    public List<ColouredPolygon> apply(List<ColouredPolygon> polygons, Random rng)
+    {
+        List<ColouredPolygon> newPolygons = new ArrayList<ColouredPolygon>(polygons.size());
+        for (ColouredPolygon polygon : polygons)
+        {
+            Color newColour = mutateColour(polygon.getColour(), rng);
+            newPolygons.add(newColour == polygon.getColour()
+                            ? polygon
+                            : new ColouredPolygon(newColour, polygon.getVertices()));
+        }
+        return newPolygons;
+    }
+
+
+    /**
+     * Mutate the specified colour.
+     * @param colour The colour to mutate.
+     * @param rng A source of randomness.
+     * @return The (possibly) mutated colour.
+     */
+    private Color mutateColour(Color colour, Random rng)
+    {
+        if (mutationProbability.nextValue().nextEvent(rng))
+        {
+            return new Color(mutateColourComponent(colour.getRed()),
+                             mutateColourComponent(colour.getGreen()),
+                             mutateColourComponent(colour.getBlue()),
+                             mutateColourComponent(colour.getAlpha()));
+        }
+        else
+        {
+            return colour;
+        }
+    }
+
+
+    /**
+     * Adjust a single component (red, green, blue or alpha) of a colour.
+     * @param component The value to mutate.
+     * @return The mutated component value.
+     */
+    private int mutateColourComponent(int component)
+    {
+        int mutatedComponent = (int) Math.round(component + mutationAmount.nextValue());
+        mutatedComponent = Maths.restrictRange(mutatedComponent, 0, 255);
+        return mutatedComponent;
+    }
+}
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/monalisa/PolygonImageEvaluator.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/monalisa/PolygonImageEvaluator.java
new file mode 100644
index 0000000..acc3e1b
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/monalisa/PolygonImageEvaluator.java
@@ -0,0 +1,158 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.monalisa;
+
+import java.awt.Dimension;
+import java.awt.geom.AffineTransform;
+import java.awt.image.AffineTransformOp;
+import java.awt.image.BufferedImage;
+import java.awt.image.Raster;
+import java.util.List;
+import org.uncommons.watchmaker.framework.FitnessEvaluator;
+import org.uncommons.watchmaker.framework.interactive.Renderer;
+
+/**
+ * Compares the generated polygon-based images to the target bitmap.  The polygon images
+ * are rendered the same size as the target image and then each pixel is compared.  The
+ * fitness value is a combination of the differences for each pixel.  Lower fitness is better. 
+ * @author Daniel Dyer
+ */
+public class PolygonImageEvaluator implements FitnessEvaluator<List<ColouredPolygon>>
+{
+    // This field is marked as transient, even though the class is not Serializable, because
+    // Terracotta will respect the fact it is transient and not try to share it.
+    private final transient ThreadLocal<Renderer<List<ColouredPolygon>, BufferedImage>> threadLocalRenderer
+        = new ThreadLocal<Renderer<List<ColouredPolygon>, BufferedImage>>();
+
+    private final int width;
+    private final int height;
+    private final AffineTransform transform;
+    private final int[] targetPixels;
+
+
+    /**
+     * Creates an evaluator that assigns fitness scores to images based on how
+     * close they are to the specified target image. 
+     * @param targetImage The image that all others are compared to.
+     */
+    public PolygonImageEvaluator(BufferedImage targetImage)
+    {
+        // Scale the image down so that its smallest dimension is 100 pixels.  For large images this drastically
+        // reduces the number of pixels that we need to check for fitness evaluation.
+        Raster targetImageData;
+        if (targetImage.getWidth() > 100 && targetImage.getHeight() > 100)
+        {
+            double ratio = 100.0d / (targetImage.getWidth() > targetImage.getHeight() ? targetImage.getHeight() : targetImage.getWidth());
+            transform = AffineTransform.getScaleInstance(ratio, ratio);
+            AffineTransformOp transformOp = new AffineTransformOp(transform,
+                                                                  AffineTransformOp.TYPE_NEAREST_NEIGHBOR);
+            targetImageData = convertImage(transformOp.filter(targetImage, null)).getData();
+        }
+        else
+        {
+            targetImageData = convertImage(targetImage).getData();
+            transform = null;
+        }
+
+        this.width = targetImageData.getWidth();
+        this.height = targetImageData.getHeight();
+        int[] pixelArray = new int[targetImageData.getWidth() * targetImageData.getHeight()];
+        targetPixels = (int[]) targetImageData.getDataElements(0,
+                                                               0,
+                                                               targetImageData.getWidth(),
+                                                               targetImageData.getHeight(),
+                                                               pixelArray);
+    }
+
+
+    /**
+     * Make sure that the image is in the most efficient format for reading from.
+     * This avoids having to convert pixels every time we access them.
+     * @param image The image to convert.
+     * @return The image converted to INT_RGB format.
+     */
+    private BufferedImage convertImage(BufferedImage image)
+    {
+        if (image.getType() == BufferedImage.TYPE_INT_RGB)
+        {
+            return image;
+        }
+        else
+        {
+            BufferedImage newImage = new BufferedImage(image.getWidth(),
+                                                       image.getHeight(),
+                                                       BufferedImage.TYPE_INT_RGB);
+            newImage.getGraphics().drawImage(image, 0, 0, null);
+            return newImage;
+        }
+    }
+
+
+    /**
+     * Render the polygons as an image and then do a pixel-by-pixel comparison
+     * against the target image.  The fitness score is the total error.  A lower
+     * score means a closer match.
+     * @param candidate The image to evaluate.
+     * @param population Not used.
+     * @return A number indicating how close the candidate image is to the target image
+     * (lower is better).
+     */
+    public double getFitness(List<ColouredPolygon> candidate,
+                             List<? extends List<ColouredPolygon>> population)
+    {
+        // Use one renderer per thread because they are not thread safe.
+        Renderer<List<ColouredPolygon>, BufferedImage> renderer = threadLocalRenderer.get();
+        if (renderer == null)
+        {
+            renderer = new PolygonImageRenderer(new Dimension(width, height),
+                                                false,
+                                                transform);
+            threadLocalRenderer.set(renderer);
+        }
+        
+        BufferedImage candidateImage = renderer.render(candidate);
+        Raster candidateImageData = candidateImage.getData();
+
+        int[] candidatePixelValues = new int[targetPixels.length];
+        candidatePixelValues = (int[]) candidateImageData.getDataElements(0,
+                                                                          0,
+                                                                          candidateImageData.getWidth(),
+                                                                          candidateImageData.getHeight(),
+                                                                          candidatePixelValues);
+        double fitness = 0;
+        for (int i = 0; i < targetPixels.length; i++)
+        {
+            fitness += comparePixels(targetPixels[i], candidatePixelValues[i]);
+        }
+
+        return fitness;
+    }
+
+
+    private double comparePixels(int p1, int p2)
+    {
+        int deltaR = ((p1 >>> 16) & 0xFF) - ((p2 >>> 16) & 0xFF);
+        int deltaG = ((p1 >>> 8) & 0xFF) - ((p2 >>> 8) & 0xFF);
+        int deltaB = (p1 & 0xFF) - (p2 & 0xFF);
+        return Math.sqrt(deltaR * deltaR + deltaG * deltaG + deltaB * deltaB);
+    }
+
+
+    public boolean isNatural()
+    {
+        return false;
+    }
+}
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/monalisa/PolygonImageFactory.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/monalisa/PolygonImageFactory.java
new file mode 100644
index 0000000..9613172
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/monalisa/PolygonImageFactory.java
@@ -0,0 +1,75 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.monalisa;
+
+import java.awt.Color;
+import java.awt.Dimension;
+import java.awt.Point;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Random;
+import org.uncommons.watchmaker.framework.factories.AbstractCandidateFactory;
+
+/**
+ * Creates random polygon-based images.
+ * @author Daniel Dyer
+ */
+public class PolygonImageFactory extends AbstractCandidateFactory<List<ColouredPolygon>>
+{
+    /**
+     * Each image must have at least 2 polygons.
+     */
+    static final int MINIMUM_POLYGON_COUNT = 2;
+
+    /**
+     * Each polygon must have at least 3 points.
+     */
+    static final int MINIMUM_VERTEX_COUNT = 3;
+
+    private final Dimension canvasSize;
+
+    /**
+     * @param canvasSize The size of the canvas on which the image will be rendered.
+     * All polygons must fit within its bounds. 
+     */
+    public PolygonImageFactory(Dimension canvasSize)
+    {
+        this.canvasSize = canvasSize;
+    }
+
+    
+    public List<ColouredPolygon> generateRandomCandidate(Random rng)
+    {
+        List<ColouredPolygon> polygons = new ArrayList<ColouredPolygon>(MINIMUM_POLYGON_COUNT);
+        for (int i = 0; i < MINIMUM_POLYGON_COUNT; i++)
+        {
+            polygons.add(createRandomPolygon(rng));
+        }
+        return polygons;
+    }
+
+
+    ColouredPolygon createRandomPolygon(Random rng)
+    {
+        List<Point> vertices = new ArrayList<Point>(MINIMUM_VERTEX_COUNT);
+        for (int j = 0; j < MINIMUM_VERTEX_COUNT; j++)
+        {
+            vertices.add(new Point(rng.nextInt(canvasSize.width), rng.nextInt(canvasSize.height)));
+        }
+        Color colour = new Color(rng.nextInt(256), rng.nextInt(256), rng.nextInt(256), rng.nextInt(256));
+        return new ColouredPolygon(colour, vertices);
+    }
+}
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/monalisa/PolygonImageRenderer.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/monalisa/PolygonImageRenderer.java
new file mode 100644
index 0000000..876c9f0
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/monalisa/PolygonImageRenderer.java
@@ -0,0 +1,91 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.monalisa;
+
+import java.awt.Color;
+import java.awt.Dimension;
+import java.awt.Graphics2D;
+import java.awt.RenderingHints;
+import java.awt.geom.AffineTransform;
+import java.awt.image.BufferedImage;
+import java.util.List;
+import org.uncommons.watchmaker.framework.interactive.Renderer;
+
+/**
+ * Renders a polygon-based image to a {@link BufferedImage}.  For efficiency reasons, this
+ * renderer returns the same image object (with different data) for subsequent invocations.
+ * This means that invoking code should not expect returned images to be unaltered following
+ * subsequent invocations.  It also means that a renderer is not thread-safe.
+ * @author Daniel Dyer
+ */
+public class PolygonImageRenderer implements Renderer<List<ColouredPolygon>, BufferedImage>
+{
+    private static final AffineTransform IDENTITY_TRANSFORM = new AffineTransform();
+    
+    private final Dimension targetSize;
+    private final AffineTransform transform;
+    private final BufferedImage image;
+    private final Graphics2D graphics;
+
+
+    /**
+     * @param targetSize The size of the canvas on which the polygons will be rendered.
+     * @param antialias Whether or not to enable anti-aliasing for the rendered image.
+     * @param transform A transformation applied to the vertices of an image's polygons
+     * before drawing to the destination image.  This transformation adjusts the image
+     * so that it fits on a canvas of the specified {@code targetSize}. 
+     */
+    public PolygonImageRenderer(Dimension targetSize,
+                                boolean antialias,
+                                AffineTransform transform)
+    {
+        this.targetSize = targetSize;
+        this.transform = transform;        
+        this.image = new BufferedImage(targetSize.width,
+                                       targetSize.height,
+                                       BufferedImage.TYPE_INT_RGB);
+        this.graphics = image.createGraphics();
+        if (antialias)
+        {
+            graphics.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
+                                      RenderingHints.VALUE_ANTIALIAS_ON);
+        }
+    }
+
+
+    /**
+     * Renders the specified polygons as an image.
+     * @param entity A collection of coloured polygons.
+     * @return An image object displaying the polygons.
+     */
+    public BufferedImage render(List<ColouredPolygon> entity)
+    {
+        // Need to set the background before applying the transform.
+        graphics.setTransform(IDENTITY_TRANSFORM);
+        graphics.setColor(Color.GRAY);
+        graphics.fillRect(0, 0, targetSize.width, targetSize.height);
+        if (transform != null)
+        {
+            graphics.setTransform(transform);
+        }
+        for (ColouredPolygon polygon : entity)
+        {
+            graphics.setColor(polygon.getColour());
+            graphics.fillPolygon(polygon.getPolygon());
+        }
+        return image;
+    }
+}
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/monalisa/PolygonImageSwingRenderer.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/monalisa/PolygonImageSwingRenderer.java
new file mode 100644
index 0000000..1ce7e05
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/monalisa/PolygonImageSwingRenderer.java
@@ -0,0 +1,143 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.monalisa;
+
+import java.awt.Dimension;
+import java.awt.FontMetrics;
+import java.awt.Graphics;
+import java.awt.image.BufferedImage;
+import java.util.List;
+import javax.swing.JComponent;
+import org.uncommons.watchmaker.framework.interactive.Renderer;
+
+/**
+ * Converts a {@link BufferedImage} to a {@link JComponent} that displays that image
+ * alongside a pre-specified target image.
+ * @author Daniel Dyer
+ */
+public class PolygonImageSwingRenderer implements Renderer<List<ColouredPolygon>, JComponent>
+{
+    private final BufferedImage targetImage;
+    private final Renderer<List<ColouredPolygon>, BufferedImage> delegate;
+
+
+    /**
+     * @param targetImage This image is displayed on the left side of the
+     * JComponent.
+     */
+    public PolygonImageSwingRenderer(BufferedImage targetImage)
+    {
+        // Convert the target image into the most efficient format for rendering.
+        this.targetImage = new BufferedImage(targetImage.getWidth(),
+                                             targetImage.getHeight(),
+                                             BufferedImage.TYPE_INT_RGB);
+        this.targetImage.getGraphics().drawImage(targetImage, 0, 0, null);
+        this.targetImage.setAccelerationPriority(1);
+
+        this.delegate = new PolygonImageRenderer(new Dimension(targetImage.getWidth(),
+                                                               targetImage.getHeight()),
+                                                 true, // Anti-alias.
+                                                 null);
+    }
+
+
+    /**
+     * Renders the specified image as a JComponent with the image on the
+     * right and the pre-specified target image on the left.
+     * @param entity The image to render on the right side of the component.
+     * @return A Swing component that displays the rendered image.
+     */
+    public JComponent render(List<ColouredPolygon> entity)
+    {
+        return new ImageComponent(entity);
+    }
+
+
+    /**
+     * Swing component for rendering a fixed size image.  If the image is smaller
+     * than the component, it is centered.
+     */
+    private final class ImageComponent extends JComponent
+    {
+        private static final int GAP = 10;
+        private static final int FOOTER = 20;
+
+        private final List<ColouredPolygon> candidate;
+        private final Dimension minimumSize;
+
+
+        ImageComponent(List<ColouredPolygon> candidate)
+        {
+            this.candidate = candidate;
+            this.minimumSize = new Dimension(targetImage.getWidth() * 2 + GAP,
+                                             targetImage.getHeight() + FOOTER);
+        }
+
+        @Override
+        public Dimension getPreferredSize()
+        {
+            return minimumSize;
+        }
+
+        @Override
+        public Dimension getMinimumSize()
+        {
+            return minimumSize;
+        }
+
+
+        @Override
+        protected void paintComponent(Graphics graphics)
+        {
+            int x = Math.max(0, (getWidth() - minimumSize.width) / 2);
+            int y = Math.max(0, (getHeight() - minimumSize.height) / 2);
+            graphics.drawImage(targetImage, x, y, this);
+            BufferedImage candidateImage = delegate.render(candidate);
+            candidateImage.setAccelerationPriority(1);
+            Graphics clip = graphics.create(x + targetImage.getWidth() + GAP,
+                                            y,
+                                            candidateImage.getWidth(),
+                                            candidateImage.getHeight() + FOOTER);
+            clip.drawImage(candidateImage, 0, 0, this);
+
+            clip.setColor(getForeground());
+            String info = candidate.size() + " polygons, " + countVertices(candidate) + " vertices";
+            FontMetrics fontMetrics = clip.getFontMetrics();
+            int width = fontMetrics.stringWidth(info);
+            int height = Math.round(fontMetrics.getLineMetrics(info, clip).getHeight());
+            clip.drawString(info,
+                            candidateImage.getWidth() - width,
+                            candidateImage.getHeight() + height);
+        }
+
+
+        /**
+         * Count the number of vertices in each polygon in the image and return
+         * the total.
+         * @param image The image to inspect.
+         * @return The total number of vertices in all polygons in the image.
+         */
+        private int countVertices(List<ColouredPolygon> image)
+        {
+            int count = 0;
+            for (ColouredPolygon polygon : image)
+            {
+                count += polygon.getVertices().size();
+            }
+            return count;
+        }
+    }
+}
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/monalisa/ProbabilitiesPanel.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/monalisa/ProbabilitiesPanel.java
new file mode 100644
index 0000000..5267be3
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/monalisa/ProbabilitiesPanel.java
@@ -0,0 +1,173 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.monalisa;
+
+import java.awt.Dimension;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Random;
+import javax.swing.JLabel;
+import javax.swing.JPanel;
+import javax.swing.SpringLayout;
+import org.uncommons.maths.number.ConstantGenerator;
+import org.uncommons.maths.random.GaussianGenerator;
+import org.uncommons.maths.random.Probability;
+import org.uncommons.swing.SpringUtilities;
+import org.uncommons.watchmaker.framework.EvolutionaryOperator;
+import org.uncommons.watchmaker.framework.operators.EvolutionPipeline;
+import org.uncommons.watchmaker.framework.operators.ListCrossover;
+import org.uncommons.watchmaker.framework.operators.ListOperator;
+import org.uncommons.watchmaker.swing.ProbabilityParameterControl;
+
+/**
+ * Panel that displays controls for the Mona Lisa example program.  These
+ * controls allow the evolution parameters to be tweaked.
+ * @author Daniel Dyer
+ */
+class ProbabilitiesPanel extends JPanel
+{
+    private static final Probability ONE_TENTH = new Probability(0.1d);
+    
+    private final ProbabilityParameterControl addPolygonControl;
+    private final ProbabilityParameterControl removePolygonControl;
+    private final ProbabilityParameterControl movePolygonControl;
+    private final ProbabilityParameterControl crossOverControl;
+    private final ProbabilityParameterControl addVertexControl;
+    private final ProbabilityParameterControl removeVertexControl;
+    private final ProbabilityParameterControl moveVertexControl;
+    private final ProbabilityParameterControl changeColourControl;
+
+
+    ProbabilitiesPanel()
+    {
+        super(new SpringLayout());
+        addPolygonControl = new ProbabilityParameterControl(Probability.ZERO,
+                                                            ONE_TENTH,
+                                                            3,
+                                                            new Probability(0.02));
+        add(new JLabel("Add Polygon: "));
+        add(addPolygonControl.getControl());
+        addPolygonControl.setDescription("For each IMAGE, the probability that a new "
+                                         + "randomly-generated polygon will be added.");
+
+        addVertexControl = new ProbabilityParameterControl(Probability.ZERO,
+                                                           ONE_TENTH,
+                                                           3,
+                                                           new Probability(0.01));
+        add(new JLabel("Add Vertex: "));
+        add(addVertexControl.getControl());
+        addVertexControl.setDescription("For each POLYGON, the probability that a new "
+                                        + "randomly-generated vertex will be added.");
+
+        removePolygonControl = new ProbabilityParameterControl(Probability.ZERO,
+                                                               ONE_TENTH,
+                                                               3,
+                                                               new Probability(0.02));
+        add(new JLabel("Remove Polygon: "));
+        add(removePolygonControl.getControl());
+        removePolygonControl.setDescription("For each IMAGE, the probability that a "
+                                            + "randomly-selected polygon will be discarded.");
+
+        removeVertexControl = new ProbabilityParameterControl(Probability.ZERO,
+                                                              ONE_TENTH,
+                                                              3,
+                                                              new Probability(0.01));
+        add(new JLabel("Remove Vertex: "));
+        add(removeVertexControl.getControl());
+        removeVertexControl.setDescription("For each POLYGON, the probability that a "
+                                           + "randomly-selected vertex will be discarded.");
+
+        movePolygonControl = new ProbabilityParameterControl(Probability.ZERO,
+                                                             ONE_TENTH,
+                                                             3,
+                                                             new Probability(0.01));
+        add(new JLabel("Reorder Polygons: "));
+        add(movePolygonControl.getControl());
+        movePolygonControl.setDescription("For each IMAGE, the probability that the z-positions "
+                                          + "of two randomly-selected polygons will be swapped.");
+
+        moveVertexControl = new ProbabilityParameterControl(Probability.ZERO,
+                                                            ONE_TENTH,
+                                                            3,
+                                                            new Probability(0.03));
+        add(new JLabel("Move Vertex: "));
+        add(moveVertexControl.getControl());
+        moveVertexControl.setDescription("For each POLYGON, the probability that a randomly-selected "
+                                         + "vertex will be displaced.");
+
+        crossOverControl = new ProbabilityParameterControl(Probability.ZERO,
+                                                           Probability.ONE,
+                                                           2,
+                                                           Probability.ONE);
+        add(new JLabel("Cross-over: "));
+        add(crossOverControl.getControl());
+        crossOverControl.setDescription("For each PAIR of parent IMAGES, the probability that "
+                                        + "2-point cross-over is applied.");
+
+        changeColourControl = new ProbabilityParameterControl(Probability.ZERO,
+                                                              ONE_TENTH,
+                                                              3,
+                                                              new Probability(0.01));
+        add(new JLabel("Change Colour: "));
+        add(changeColourControl.getControl());
+        changeColourControl.setDescription("For each POLYGON, the probability that its colour will be mutated.");
+
+        // Set component names for easy look-up from tests.
+        addPolygonControl.getControl().setName("AddPolygon");
+        removePolygonControl.getControl().setName("RemovePolygon");
+        movePolygonControl.getControl().setName("MovePolygon");
+        crossOverControl.getControl().setName("Cross-over");
+        addVertexControl.getControl().setName("AddVertex");
+        removeVertexControl.getControl().setName("RemoveVertex");
+        moveVertexControl.getControl().setName("MoveVertex");
+        changeColourControl.getControl().setName("ChangeColour");
+
+        SpringUtilities.makeCompactGrid(this, 4, 4, 10, 0, 10, 0);
+    }
+
+
+    /**
+     * Construct the combination of evolutionary operators that will be used to evolve the
+     * polygon-based images.
+     * @param factory A source of polygons.
+     * @param canvasSize The size of the target image.
+     * @param rng A source of randomness.
+     * @return A complex evolutionary operator constructed from simpler operators.
+     */
+    public EvolutionaryOperator<List<ColouredPolygon>> createEvolutionPipeline(PolygonImageFactory factory,
+                                                                               Dimension canvasSize,
+                                                                               Random rng)
+    {
+        List<EvolutionaryOperator<List<ColouredPolygon>>> operators
+            = new LinkedList<EvolutionaryOperator<List<ColouredPolygon>>>();
+        operators.add(new ListCrossover<ColouredPolygon>(new ConstantGenerator<Integer>(2),
+                                                         crossOverControl.getNumberGenerator()));
+        operators.add(new RemovePolygonMutation(removePolygonControl.getNumberGenerator()));
+        operators.add(new MovePolygonMutation(movePolygonControl.getNumberGenerator()));
+        operators.add(new ListOperator<ColouredPolygon>(new RemoveVertexMutation(canvasSize,
+                                                                                 removeVertexControl.getNumberGenerator())));
+        operators.add(new ListOperator<ColouredPolygon>(new AdjustVertexMutation(canvasSize,
+                                                                                 moveVertexControl.getNumberGenerator(),
+                                                                                 new GaussianGenerator(0, 3, rng))));
+        operators.add(new ListOperator<ColouredPolygon>(new AddVertexMutation(canvasSize,
+                                                                              addVertexControl.getNumberGenerator())));
+        operators.add(new ListOperator<ColouredPolygon>(new PolygonColourMutation(changeColourControl.getNumberGenerator(),
+                                                                                  new GaussianGenerator(0, 20, rng))));
+        operators.add(new AddPolygonMutation(addPolygonControl.getNumberGenerator(), factory, 50));
+        return new EvolutionPipeline<List<ColouredPolygon>>(operators);
+    }
+
+}
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/monalisa/RemovePolygonMutation.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/monalisa/RemovePolygonMutation.java
new file mode 100644
index 0000000..d1d33bb
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/monalisa/RemovePolygonMutation.java
@@ -0,0 +1,75 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.monalisa;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Random;
+import org.uncommons.maths.number.ConstantGenerator;
+import org.uncommons.maths.number.NumberGenerator;
+import org.uncommons.maths.random.Probability;
+import org.uncommons.watchmaker.framework.EvolutionaryOperator;
+
+/**
+ * Randomly mutates the polygons that make up an image by removing a polygon
+ * according to some probability.
+ * @author Daniel Dyer
+ */
+public class RemovePolygonMutation implements EvolutionaryOperator<List<ColouredPolygon>>
+{
+    private final NumberGenerator<Probability> removePolygonProbability;
+
+    /**
+     * @param removePolygonProbability A {@link NumberGenerator} that controls the probability
+     * that a polygon will be removed.
+     */
+    public RemovePolygonMutation(NumberGenerator<Probability> removePolygonProbability)
+    {
+        this.removePolygonProbability = removePolygonProbability;
+    }
+
+
+    /**
+     * @param removePolygonProbability The probability that a polygon will be removed.
+     */
+    public RemovePolygonMutation(Probability removePolygonProbability)
+    {
+        this(new ConstantGenerator<Probability>(removePolygonProbability));
+    }
+
+
+    public List<List<ColouredPolygon>> apply(List<List<ColouredPolygon>> selectedCandidates, Random rng)
+    {
+        List<List<ColouredPolygon>> mutatedCandidates = new ArrayList<List<ColouredPolygon>>(selectedCandidates.size());
+        for (List<ColouredPolygon> candidate : selectedCandidates)
+        {
+            // A single polygon is removed with the configured probability, unless
+            // we already have the minimum permitted number of polygons.
+            if (candidate.size() > PolygonImageFactory.MINIMUM_POLYGON_COUNT
+                && removePolygonProbability.nextValue().nextEvent(rng))
+            {
+                List<ColouredPolygon> newPolygons = new ArrayList<ColouredPolygon>(candidate);
+                newPolygons.remove(rng.nextInt(newPolygons.size()));
+                mutatedCandidates.add(newPolygons);
+            }
+            else // Nothing changed.
+            {
+                mutatedCandidates.add(candidate);
+            }
+        }
+        return mutatedCandidates;
+    }
+}
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/monalisa/RemoveVertexMutation.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/monalisa/RemoveVertexMutation.java
new file mode 100644
index 0000000..4ec530d
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/monalisa/RemoveVertexMutation.java
@@ -0,0 +1,76 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.monalisa;
+
+import java.awt.Dimension;
+import java.awt.Point;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Random;
+import org.uncommons.maths.number.ConstantGenerator;
+import org.uncommons.maths.number.NumberGenerator;
+import org.uncommons.maths.random.Probability;
+
+/**
+ * Evolutionary operator for mutating individual polygons.  Polygons are mutated
+ * by removing a point, according to some probability.
+ * @author Daniel Dyer
+ */
+public class RemoveVertexMutation extends AbstractVertexMutation
+{
+    /**
+     * @param mutationProbability A {@link NumberGenerator} that controls the
+     * probability that a point will be removed.
+     * @param canvasSize The size of the canvas.  Used to constrain the positions
+     * of the points.
+     */
+    public RemoveVertexMutation(Dimension canvasSize,
+                                NumberGenerator<Probability> mutationProbability)
+    {
+        super(mutationProbability, canvasSize);
+    }
+
+
+    /**
+     * @param mutationProbability The probability that a point will be removed.
+     * @param canvasSize The size of the canvas.  Used to constrain the positions
+     * of the points.
+     */
+    public RemoveVertexMutation(Dimension canvasSize,
+                                Probability mutationProbability)
+    {
+        this(canvasSize, new ConstantGenerator<Probability>(mutationProbability));
+    }
+
+
+    @Override
+    protected List<Point> mutateVertices(List<Point> vertices, Random rng)
+    {
+        // A single point is removed with the configured probability, unless
+        // we already have the minimum permitted number of points.
+        if (vertices.size() > PolygonImageFactory.MINIMUM_VERTEX_COUNT
+            && getMutationProbability().nextValue().nextEvent(rng))
+        {
+            List<Point> newVertices = new ArrayList<Point>(vertices);
+            newVertices.remove(rng.nextInt(newVertices.size()));
+            return newVertices;
+        }
+        else // Nothing changed.
+        {
+            return vertices;
+        }
+    }
+}
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/monalisa/package-info.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/monalisa/package-info.java
new file mode 100644
index 0000000..1602c91
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/monalisa/package-info.java
@@ -0,0 +1,23 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+/**
+ * An evolutionary art example application inspired by Roger Alsing's evolution of the
+ * Mona Lisa (http://rogeralsing.com/2008/12/07/genetic-programming-evolution-of-mona-lisa/).
+ * It attempts to find the combination of 50 translucent polygons that most closely
+ * resembles Leonardo da Vinci's Mona Lisa.
+ * @author Daniel Dyer
+ */
+package org.uncommons.watchmaker.examples.monalisa;
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/strings/StringEvaluator.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/strings/StringEvaluator.java
new file mode 100644
index 0000000..ac56c9f
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/strings/StringEvaluator.java
@@ -0,0 +1,73 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.strings;
+
+import java.util.List;
+import org.uncommons.watchmaker.framework.FitnessEvaluator;
+
+/**
+ * Evaluates strings and assigns a fitness score based on how many characters
+ * differ from the equivalent positions in a given target string.
+ * @author Daniel Dyer
+ */
+public class StringEvaluator implements FitnessEvaluator<String>
+{
+    private final String targetString;
+
+
+    /**
+     * Creates a {@link FitnessEvaluator} that calculates scores
+     * for Strings based on how close they are to a target String.
+     * @param targetString The target of the evolution.
+     */
+    public StringEvaluator(String targetString)
+    {
+        this.targetString = targetString;
+    }
+
+
+    /**
+     * Assigns one "penalty point" for every character in the candidate
+     * string that differs from the corresponding position in the target
+     * string.
+     * @param candidate The evolved string to evaluate.
+     * @param population {@inheritDoc}
+     * @return The fitness score (how many characters are wrong) of the
+     * specified string.
+     */
+    public double getFitness(String candidate,
+                             List<? extends String> population)
+    {
+        int errors = 0;
+        for (int i = 0; i < candidate.length(); i++)
+        {
+            if (candidate.charAt(i) != targetString.charAt(i))
+            {
+                ++errors;
+            }
+        }
+        return errors;
+    }
+
+
+    /**
+     * {@inheritDoc}
+     */
+    public boolean isNatural()
+    {
+        return false;
+    }
+}
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/strings/StringsExample.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/strings/StringsExample.java
new file mode 100644
index 0000000..d8425fa
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/strings/StringsExample.java
@@ -0,0 +1,119 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.strings;
+
+import java.util.ArrayList;
+import java.util.List;
+import org.uncommons.maths.random.MersenneTwisterRNG;
+import org.uncommons.maths.random.Probability;
+import org.uncommons.watchmaker.framework.EvolutionEngine;
+import org.uncommons.watchmaker.framework.EvolutionObserver;
+import org.uncommons.watchmaker.framework.EvolutionaryOperator;
+import org.uncommons.watchmaker.framework.GenerationalEvolutionEngine;
+import org.uncommons.watchmaker.framework.PopulationData;
+import org.uncommons.watchmaker.framework.factories.StringFactory;
+import org.uncommons.watchmaker.framework.operators.EvolutionPipeline;
+import org.uncommons.watchmaker.framework.operators.StringCrossover;
+import org.uncommons.watchmaker.framework.operators.StringMutation;
+import org.uncommons.watchmaker.framework.selection.RouletteWheelSelection;
+import org.uncommons.watchmaker.framework.termination.TargetFitness;
+
+/**
+ * Simple evolutionary algorithm that evolves a population of randomly-generated
+ * strings until at least one matches a specified target string.
+ * @author Daniel Dyer
+ */
+public final class StringsExample
+{
+    private static final char[] ALPHABET = new char[27];
+    static
+    {
+        for (char c = 'A'; c <= 'Z'; c++)
+        {
+            ALPHABET[c - 'A'] = c;
+        }
+        ALPHABET[26] = ' ';
+    }
+
+
+    /**
+     * Entry point for the sample application.  Any data specified on the
+     * command line is considered to be the target String.  If no target is
+     * specified, a default of "HELLOW WORLD" is used instead.
+     * @param args The target String (as an array of words).
+     */
+    public static void main(String[] args)
+    {
+        String target = args.length == 0 ? "HELLO WORLD" : convertArgs(args);
+        String result = evolveString(target);
+        System.out.println("Evolution result: " + result);
+    }
+
+
+    public static String evolveString(String target)
+    {
+        StringFactory factory = new StringFactory(ALPHABET, target.length());
+        List<EvolutionaryOperator<String>> operators = new ArrayList<EvolutionaryOperator<String>>(2);
+        operators.add(new StringMutation(ALPHABET, new Probability(0.02d)));
+        operators.add(new StringCrossover());
+        EvolutionaryOperator<String> pipeline = new EvolutionPipeline<String>(operators);
+        EvolutionEngine<String> engine = new GenerationalEvolutionEngine<String>(factory,
+                                                                                 pipeline,
+                                                                                 new StringEvaluator(target),
+                                                                                 new RouletteWheelSelection(),
+                                                                                 new MersenneTwisterRNG());
+        engine.addEvolutionObserver(new EvolutionLogger());
+        return engine.evolve(100, // 100 individuals in the population.
+                             5, // 5% elitism.
+                             new TargetFitness(0, false));
+    }
+
+
+    /**
+     * Converts an arguments array into a single String of words
+     * separated by spaces.
+     * @param args The command-line arguments.
+     * @return A single String made from the command line data.
+     */
+    private static String convertArgs(String[] args)
+    {
+        StringBuilder result = new StringBuilder();
+        for (int i = 0; i < args.length; i++)
+        {
+            result.append(args[i]);
+            if (i < args.length - 1)
+            {
+                result.append(' ');
+            }
+        }
+        return result.toString().toUpperCase();
+    }
+
+
+    /**
+     * Trivial evolution observer for displaying information at the end
+     * of each generation.
+     */
+    private static class EvolutionLogger implements EvolutionObserver<String>
+    {
+        public void populationUpdate(PopulationData<? extends String> data)
+        {
+            System.out.printf("Generation %d: %s\n",
+                              data.getGenerationNumber(),
+                              data.getBestCandidate());
+        }
+    }
+}
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/strings/package-info.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/strings/package-info.java
new file mode 100644
index 0000000..f5f4489
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/strings/package-info.java
@@ -0,0 +1,22 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+/**
+ * Simple example that demonstrates how to use the evolution framework.
+ * Evolves candidates of type String, attempting to find a particular
+ * target phrase.
+ * @author Daniel Dyer
+ */
+package org.uncommons.watchmaker.examples.strings;
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/sudoku/Sudoku.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/sudoku/Sudoku.java
new file mode 100644
index 0000000..9319177
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/sudoku/Sudoku.java
@@ -0,0 +1,150 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.sudoku;
+
+/**
+ * A potential solution for a Sudoku puzzle.
+ * @author Daniel Dyer
+ */
+public final class Sudoku
+{
+    /** The dimensions (in cells) of the puzzle square. */
+    public static final int SIZE = 9;
+    private static final int MIN_VALUE = 1;
+    private static final int MAX_VALUE = SIZE;
+
+    private final Cell[][] cells;
+
+
+    /**
+     * Creates a sudoku solution from a 2-dimensional array of cells.
+     * @param cells The cells that make-up this Sudoku grid.
+     */
+    public Sudoku(Cell[][] cells)
+    {
+        if (cells.length != SIZE)
+        {
+            throw new IllegalArgumentException("Sudoku must have 9 rows.");
+        }
+        if (cells[0].length != SIZE) // Should really check all rows because the array may not be square.
+        {
+            throw new IllegalArgumentException("Sudoku must have 9 columns.");
+        }
+        this.cells = cells;
+    }
+
+
+    /**
+     * Queries the value of a particular cell.
+     * @param row The row index of the cell.
+     * @param column The column index of the cell.
+     * @return The value (1 - 9) of the specified cell.
+     */
+    public int getValue(int row, int column)
+    {
+        return cells[row][column].getValue();
+    }
+
+
+    /**
+     * Checks whether a particular cell is a 'given' or not. 
+     * @param row The row index of the cell.
+     * @param column The column index of the cell.
+     * @return True if the value in the identified cell is fixed (a 'given' cell),
+     * false otherwise.
+     */
+    public boolean isFixed(int row, int column)
+    {
+        return cells[row][column].isFixed();
+    }
+
+
+    /**
+     * Returns an array of cells that make up a row.  The array
+     * returned is a clone of the underlying data structure and
+     * therefore can be modified without affecting this object.
+     * @param row The index of the row to return.
+     * @return A row of cells from this Sudoku grid.
+     */
+    public Cell[] getRow(int row)
+    {
+        return cells[row].clone();
+    }
+
+
+    /**
+     * Renders the Sudoku grid as a multi-line String.
+     * @return The String representation of this grid.
+     */
+    @Override
+    public String toString()
+    {
+        StringBuilder buffer = new StringBuilder();
+        for (Cell[] row : cells)
+        {
+            for (Cell cell : row)
+            {
+                buffer.append(' ');
+                buffer.append(cell.getValue());
+            }
+            buffer.append('\n');
+        }
+        return buffer.toString();
+    }
+
+
+    /**
+     * A single cell in a sudoku grid.  Contains a value and may be fixed (i.e. it is
+     * one of the given cells at the start).
+     */
+    public static final class Cell
+    {
+        private final int value;
+        private final boolean fixed;
+
+        /**
+         * @param value The value (1 - 9) contained in this cell.
+         * @param fixed Whether or not this cell's value is fixed (a 'given').
+         */
+        public Cell(int value, boolean fixed)
+        {
+            if (value < MIN_VALUE || value > MAX_VALUE)
+            {
+                throw new IllegalArgumentException("Value must be between 1 and 9.");
+            }
+            this.value = value;
+            this.fixed = fixed;
+        }
+
+
+        /**
+         * @return The value contained in this cell.
+         */
+        public int getValue()
+        {
+            return value;
+        }
+
+
+        /**
+         * @return True if this cell is a 'given', false otherwise.
+         */
+        public boolean isFixed()
+        {
+            return fixed;
+        }
+    }
+}
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/sudoku/SudokuApplet.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/sudoku/SudokuApplet.java
new file mode 100644
index 0000000..2a856e9
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/sudoku/SudokuApplet.java
@@ -0,0 +1,283 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.sudoku;
+
+import java.awt.BorderLayout;
+import java.awt.Container;
+import java.awt.FlowLayout;
+import java.awt.event.ActionEvent;
+import java.awt.event.ActionListener;
+import java.awt.event.ItemEvent;
+import java.awt.event.ItemListener;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Random;
+import java.util.concurrent.TimeUnit;
+import javax.swing.BorderFactory;
+import javax.swing.JButton;
+import javax.swing.JComboBox;
+import javax.swing.JComponent;
+import javax.swing.JLabel;
+import javax.swing.JPanel;
+import javax.swing.JSpinner;
+import javax.swing.SpinnerNumberModel;
+import javax.swing.SpringLayout;
+import javax.swing.SwingUtilities;
+import org.uncommons.maths.random.DiscreteUniformGenerator;
+import org.uncommons.maths.random.MersenneTwisterRNG;
+import org.uncommons.maths.random.PoissonGenerator;
+import org.uncommons.maths.random.Probability;
+import org.uncommons.swing.SpringUtilities;
+import org.uncommons.swing.SwingBackgroundTask;
+import org.uncommons.watchmaker.examples.AbstractExampleApplet;
+import org.uncommons.watchmaker.framework.EvolutionEngine;
+import org.uncommons.watchmaker.framework.EvolutionObserver;
+import org.uncommons.watchmaker.framework.EvolutionaryOperator;
+import org.uncommons.watchmaker.framework.GenerationalEvolutionEngine;
+import org.uncommons.watchmaker.framework.PopulationData;
+import org.uncommons.watchmaker.framework.SelectionStrategy;
+import org.uncommons.watchmaker.framework.operators.EvolutionPipeline;
+import org.uncommons.watchmaker.framework.selection.TournamentSelection;
+import org.uncommons.watchmaker.framework.termination.TargetFitness;
+import org.uncommons.watchmaker.swing.AbortControl;
+import org.uncommons.watchmaker.swing.ProbabilityParameterControl;
+import org.uncommons.watchmaker.swing.SwingEvolutionObserver;
+import org.uncommons.watchmaker.swing.evolutionmonitor.StatusBar;
+
+/**
+ * An evolutionary Sudoku solver.
+ * @author Daniel Dyer
+ */
+public class SudokuApplet extends AbstractExampleApplet
+{
+    private static final String[] BLANK_PUZZLE = {".........",
+                                                  ".........",
+                                                  ".........",
+                                                  ".........",
+                                                  ".........",
+                                                  ".........",
+                                                  ".........",
+                                                  ".........",
+                                                  "........."};
+
+    private static final String[] EASY_PUZZLE = {"4.5...9.7",
+                                                 ".2..9..6.",
+                                                 "39.6.7.28",
+                                                 "9..3.2..6",
+                                                 "7..9.6..3",
+                                                 "5..4.8..1",
+                                                 "28.1.5.49",
+                                                 ".7..3..8.",
+                                                 "6.4...3.2"};
+
+    private static final String[] MEDIUM_PUZZLE = {"....3....",
+                                                   ".....6293",
+                                                   ".2.9.48..",
+                                                   ".754...38",
+                                                   "..46.71..",
+                                                   "91...547.",
+                                                   "..38.9.1.",
+                                                   "1567.....",
+                                                   "....1...."};
+
+    private static final String[] HARD_PUZZLE = {"...891...",
+                                                 "....5.8..",
+                                                 ".....6.2.",
+                                                 "5....4..8",
+                                                 "49....67.",
+                                                 "8.13....5",
+                                                 ".6..8..9.",
+                                                 "..5.4.2.7",
+                                                 "...1.3.8."};
+
+    private static final String[][] PUZZLES = {EASY_PUZZLE,
+                                               MEDIUM_PUZZLE,
+                                               HARD_PUZZLE,
+                                               BLANK_PUZZLE};
+
+    private SelectionStrategy<Object> selectionStrategy;
+
+    private SudokuView sudokuView;
+    private JButton solveButton;
+    private JComboBox puzzleCombo;
+    private JSpinner populationSizeSpinner;
+    private AbortControl abortControl;
+    private StatusBar statusBar;
+
+
+    /**
+     * Initialise and layout the GUI.
+     * @param container The Swing component that will contain the GUI controls.
+     */
+    @Override
+    protected void prepareGUI(Container container)
+    {
+        sudokuView = new SudokuView();
+        container.add(createControls(), BorderLayout.NORTH);
+        container.add(sudokuView, BorderLayout.CENTER);
+        statusBar = new StatusBar();
+        container.add(statusBar, BorderLayout.SOUTH);
+        sudokuView.setPuzzle(EASY_PUZZLE);
+    }
+
+
+    private JComponent createControls()
+    {
+        JPanel controls = new JPanel(new BorderLayout());
+        JPanel innerPanel = new JPanel(new SpringLayout());
+        innerPanel.add(new JLabel("Puzzle: "));
+        puzzleCombo = new JComboBox(new String[]{"Easy Demo (38 givens)",
+                                                 "Medium Demo (32 givens)",
+                                                 "Hard Demo (28 givens)",
+                                                 "Custom"});
+        innerPanel.add(puzzleCombo);
+        puzzleCombo.addItemListener(new ItemListener()
+        {
+            public void itemStateChanged(ItemEvent ev)
+            {
+                sudokuView.setPuzzle(PUZZLES[puzzleCombo.getSelectedIndex()]);
+            }
+        });
+        innerPanel.add(new JLabel("Selection Pressure: "));
+        ProbabilityParameterControl selectionPressure = new ProbabilityParameterControl(Probability.EVENS,
+                                                                                        Probability.ONE,
+                                                                                        2,
+                                                                                        new Probability(0.85d));
+
+        selectionStrategy = new TournamentSelection(selectionPressure.getNumberGenerator());
+        innerPanel.add(selectionPressure.getControl());
+        innerPanel.add(new JLabel("Population Size: "));
+        populationSizeSpinner = new JSpinner(new SpinnerNumberModel(500, 10, 50000, 1));
+        innerPanel.add(populationSizeSpinner);
+        SpringUtilities.makeCompactGrid(innerPanel, 3, 2, 0, 6, 6, 6);
+        innerPanel.setBorder(BorderFactory.createTitledBorder("Configuration"));
+        controls.add(innerPanel, BorderLayout.CENTER);
+        controls.add(createButtonPanel(), BorderLayout.SOUTH);
+        return controls;
+    }
+
+
+    private JComponent createButtonPanel()
+    {
+        JPanel buttonPanel = new JPanel(new FlowLayout());
+        solveButton = new JButton("Solve");
+        solveButton.addActionListener(new ActionListener()
+        {
+            public void actionPerformed(ActionEvent ev)
+            {
+                int populationSize = (Integer) populationSizeSpinner.getValue();
+                puzzleCombo.setEnabled(false);
+                populationSizeSpinner.setEnabled(false);
+                solveButton.setEnabled(false);
+                abortControl.reset();
+                createTask(sudokuView.getPuzzle(),
+                           populationSize,
+                           (int) Math.round(populationSize * 0.05)).execute(); // Elite count is 5%.
+            }
+        });
+
+        buttonPanel.add(solveButton);
+        abortControl = new AbortControl();
+        buttonPanel.add(abortControl.getControl());
+        abortControl.getControl().setEnabled(false);
+        return buttonPanel;
+    }
+
+
+    /**
+     * Helper method to create a background task for running the interactive evolutionary
+     * algorithm.
+     * @return A Swing task that will execute on a background thread and update
+     * the GUI when it is done.
+     */
+    private SwingBackgroundTask<Sudoku> createTask(final String[] puzzle,
+                                                   final int populationSize,
+                                                   final int eliteCount)
+    {
+        return new SwingBackgroundTask<Sudoku>()
+        {
+            @Override
+            protected Sudoku performTask()
+            {
+                Random rng = new MersenneTwisterRNG();
+                List<EvolutionaryOperator<Sudoku>> operators = new ArrayList<EvolutionaryOperator<Sudoku>>(2);
+                // Cross-over rows between parents (so offspring is x rows from parent1 and
+                // y rows from parent2).
+                operators.add(new SudokuVerticalCrossover());
+                // Mutate the order of cells within individual rows.
+                operators.add(new SudokuRowMutation(new PoissonGenerator(2, rng),
+                                                    new DiscreteUniformGenerator(1, 8, rng)));
+
+                EvolutionaryOperator<Sudoku> pipeline = new EvolutionPipeline<Sudoku>(operators);
+
+                EvolutionEngine<Sudoku> engine = new GenerationalEvolutionEngine<Sudoku>(new SudokuFactory(puzzle),
+                                                                                         pipeline,
+                                                                                         new SudokuEvaluator(),
+                                                                                         selectionStrategy,
+                                                                                         rng);
+                engine.addEvolutionObserver(new SwingEvolutionObserver<Sudoku>(new GridViewUpdater(),
+                                                                               100,
+                                                                               TimeUnit.MILLISECONDS));
+                engine.addEvolutionObserver(statusBar);
+                return engine.evolve(populationSize,
+                                     eliteCount,
+                                     new TargetFitness(0, false), // Continue until a perfect solution is found...
+                                     abortControl.getTerminationCondition()); // ...or the user aborts.
+            }
+
+
+            @Override
+            protected void postProcessing(Sudoku result)
+            {
+                puzzleCombo.setEnabled(true);
+                populationSizeSpinner.setEnabled(true);
+                solveButton.setEnabled(true);
+                abortControl.getControl().setEnabled(false);
+            }
+        };
+    }
+
+
+
+    /**
+     * Evolution observer for displaying information at the end of
+     * each generation.
+     */
+    private class GridViewUpdater implements EvolutionObserver<Sudoku>
+    {
+        public void populationUpdate(final PopulationData<? extends Sudoku> data)
+        {
+            SwingUtilities.invokeLater(new Runnable()
+            {
+                public void run()
+                {
+                    sudokuView.setSolution(data.getBestCandidate());
+                }
+            });
+        }
+    }
+
+
+    /**
+     * Entry point for running this example as an application rather than an applet.
+     * @param args Program arguments (ignored).
+     */
+    public static void main(String[] args)
+    {
+        new SudokuApplet().displayInFrame("Watchmaker Framework - Sudoku Example");
+    }
+
+}
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/sudoku/SudokuCellRenderer.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/sudoku/SudokuCellRenderer.java
new file mode 100644
index 0000000..ebfa15a
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/sudoku/SudokuCellRenderer.java
@@ -0,0 +1,162 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.sudoku;
+
+import java.awt.Color;
+import java.awt.Component;
+import java.awt.Font;
+import javax.swing.JComponent;
+import javax.swing.JLabel;
+import javax.swing.JTable;
+import javax.swing.border.Border;
+import javax.swing.table.DefaultTableCellRenderer;
+import org.uncommons.swing.ConfigurableLineBorder;
+
+/**
+ * Renders Sudoku cells in a JTable.  As well as displaying the cell value,
+ * grid lines are drawn to conform to normal Sudoku conventions and incorrect
+ * solutions have their invalid cells colour-coded.
+ * @author Daniel Dyer
+ */
+class SudokuCellRenderer extends DefaultTableCellRenderer
+{
+    private static final Font VARIABLE_CELL_FONT = new Font("Monospaced", Font.PLAIN, 32);
+    private static final Font FIXED_CELL_FONT = new Font("Monospaced", Font.BOLD, 34);
+    private static final Color VARIABLE_TEXT_COLOUR = Color.DARK_GRAY;
+    private static final Color FIXED_TEXT_COLOUR = Color.BLACK;
+
+    private static final Color[] CONFLICT_COLOURS = {Color.WHITE, Color.YELLOW, Color.ORANGE, Color.RED};
+
+    private static final Border TOP_BORDER = new ConfigurableLineBorder(true, false, false, false, 1);
+    private static final Border BOTTOM_BORDER = new ConfigurableLineBorder(false, false, true, false, 1);
+    private static final Border LEFT_BORDER = new ConfigurableLineBorder(false, true, false, false, 1);
+    private static final Border RIGHT_BORDER = new ConfigurableLineBorder(false, false, false, true, 1);
+    private static final Border TOP_LEFT_BORDER = new ConfigurableLineBorder(true, true, false, false, 1);
+    private static final Border TOP_RIGHT_BORDER = new ConfigurableLineBorder(true, false, false, true, 1);
+    private static final Border BOTTOM_LEFT_BORDER = new ConfigurableLineBorder(false, true, true, false, 1);
+    private static final Border BOTTOM_RIGHT_BORDER = new ConfigurableLineBorder(false, false, true, true, 1);
+
+
+    SudokuCellRenderer()
+    {
+        setHorizontalAlignment(JLabel.CENTER);
+    }
+
+
+    @Override
+    public Component getTableCellRendererComponent(JTable table,
+                                                   Object value,
+                                                   boolean isSelected,
+                                                   boolean hasFocus,
+                                                   int row,
+                                                   int column)
+    {
+        Component component = super.getTableCellRendererComponent(table,
+                                                                  value,
+                                                                  false,
+                                                                  false,
+                                                                  row,
+                                                                  column);
+        SudokuTableModel model = (SudokuTableModel) table.getModel();
+        Sudoku sudoku = model.getSudoku();
+        if (sudoku != null)
+        {
+            if (sudoku.isFixed(row, column))
+            {
+                component.setFont(FIXED_CELL_FONT);
+                component.setForeground(FIXED_TEXT_COLOUR);
+            }
+            else
+            {
+                component.setFont(VARIABLE_CELL_FONT);
+                component.setForeground(VARIABLE_TEXT_COLOUR);
+            }
+
+            int conflicts = 0;
+            // Calculate conflicts in columns (there should be no conflicts in rows
+            // because of the constraints enforced by the evolutionary operators).
+            for (int i = 0; i < Sudoku.SIZE; i++)
+            {
+                if (i != row && model.getValueAt(i, column).equals(value))
+                {
+                    ++conflicts;
+                }
+            }
+            // Calculate conflicts in sub-grid.
+            int band = row / 3;
+            int bandStart = band * 3;
+            int stack = column / 3;
+            int stackStart = stack * 3;
+            for (int i = bandStart; i < bandStart + 3; i++)
+            {
+                for (int j = stackStart; j < stackStart + 3; j++)
+                {
+                    if (i != row && j != column && model.getValueAt(i, j).equals(value))
+                    {
+                        ++conflicts;
+                    }
+                }
+            }
+
+            // Color the cell based on how "wrong" it is.
+            component.setBackground(CONFLICT_COLOURS[Math.min(conflicts, CONFLICT_COLOURS.length - 1)]);
+        }
+        else
+        {
+            // If the model is in puzzle mode, then all non-null cells are 'givens'.
+            component.setFont(FIXED_CELL_FONT);
+            component.setForeground(FIXED_TEXT_COLOUR);
+        }
+
+        ((JComponent) component).setBorder(getBorder(row, column));
+
+
+        return component;
+    }
+
+
+    /**
+     * Get appropriate border for cell based on its position in the grid.
+     */
+    private Border getBorder(int row, int column)
+    {
+        if (row % 3 == 2)
+        {
+            switch (column % 3)
+            {
+                case 2: return BOTTOM_RIGHT_BORDER;
+                case 0: return BOTTOM_LEFT_BORDER;
+                default: return BOTTOM_BORDER;
+            }
+        }
+        else if (row % 3 == 0)
+        {
+            switch (column % 3)
+            {
+                case 2: return TOP_RIGHT_BORDER;
+                case 0: return TOP_LEFT_BORDER;
+                default: return TOP_BORDER;
+            }
+        }
+
+        switch (column % 3)
+        {
+            case 2: return RIGHT_BORDER;
+            case 0: return LEFT_BORDER;
+            default: return null;
+        }
+    }
+}
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/sudoku/SudokuEvaluator.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/sudoku/SudokuEvaluator.java
new file mode 100644
index 0000000..ca44394
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/sudoku/SudokuEvaluator.java
@@ -0,0 +1,89 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.sudoku;
+
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+import org.uncommons.watchmaker.framework.FitnessEvaluator;
+
+/**
+ * {@link org.uncommons.watchmaker.framework.FitnessEvaluator} for potential Sudoku
+ * solutions.  Counts the number of duplicate values in rows, columns and sub-grids.
+ * The fitness score is the total number of duplicate values.  Therefore, a fitness
+ * score of zero indicates a perfect solution. 
+ * @author Daniel Dyer
+ */
+public class SudokuEvaluator implements FitnessEvaluator<Sudoku>
+{
+    /**
+     * The fitness score for a potential Sudoku solution is the number of
+     * cells that conflict with other cells in the grid (i.e. if there are
+     * two 7s in the same column, both of these cells are conflicting).  A
+     * lower score indicates a fitter individual.
+     * @param candidate The Sudoku grid to evaluate.
+     * @param population {@inheritDoc}
+     * @return The fitness score for the specified individual.
+     */
+    public double getFitness(Sudoku candidate,
+                             List<? extends Sudoku> population)
+    {
+        // We can assume that there are no duplicates in any rows because
+        // the candidate factory and evolutionary operators that we use do
+        // not permit rows to contain duplicates.
+
+        int fitness = 0;
+
+        // Check columns for duplicates.
+        Set<Integer> values = new HashSet<Integer>(Sudoku.SIZE * 2); // Big enough to avoid re-hashing.
+        for (int column = 0; column < Sudoku.SIZE; column++)
+        {
+            for (int row = 0; row < Sudoku.SIZE; row++)
+            {
+                values.add(candidate.getValue(row, column));
+            }
+            fitness += (Sudoku.SIZE - values.size());
+            values.clear();
+        }
+
+        // Check sub-grids for duplicates.
+        for (int band = 0; band < Sudoku.SIZE; band += 3)
+        {
+            for (int stack = 0; stack < Sudoku.SIZE; stack += 3)
+            {
+                for (int row = band; row < band + 3; row++)
+                {
+                    for (int column = stack; column < stack + 3; column++)
+                    {
+                        values.add(candidate.getValue(row, column));
+                    }
+                }
+                fitness += (Sudoku.SIZE - values.size());
+                values.clear();
+            }
+        }
+        return fitness;
+    }
+
+
+    /**
+     * @return false
+     */
+    public boolean isNatural()
+    {
+        return false;
+    }
+}
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/sudoku/SudokuFactory.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/sudoku/SudokuFactory.java
new file mode 100644
index 0000000..d96ed1a
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/sudoku/SudokuFactory.java
@@ -0,0 +1,125 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.sudoku;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+import java.util.Random;
+import org.uncommons.watchmaker.framework.factories.AbstractCandidateFactory;
+
+/**
+ * Factory that generates potential Sudoku solutions from a list of "givens".
+ * The rows of the generated solutions will all be valid (i.e. no duplicate values)
+ * but there are no constraints on the columns or sub-grids (these will be refined
+ * by the evolutionary algorithm).
+ * @author Daniel Dyer
+ */
+public class SudokuFactory extends AbstractCandidateFactory<Sudoku>
+{
+    private static final List<Integer> VALUES = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9);
+
+    private final Sudoku.Cell[][] template;
+    private final List<List<Integer>> nonFixedValues = new ArrayList<List<Integer>>(Sudoku.SIZE);
+
+
+    /**
+     * Creates a factory for generating random candidate solutions
+     * for a specified Sudoku puzzle.
+     * @param pattern An array of Strings.  Each element represents
+     * one row in the puzzle.  Each character represents a single
+     * cell.  Permitted characters are the digits '1' to '9' (each
+     * of which represents a fixed cell in the pattern) or the '.'
+     * character, which represents an empty cell.
+     * @throws IllegalArgumentException If {@literal pattern} does not
+     * consist of nine Strings with nine characters ('0' to '9', or '.')
+     * in each.
+     */
+    public SudokuFactory(String... pattern)
+    {
+        if (pattern.length != Sudoku.SIZE)
+        {
+            throw new IllegalArgumentException("Sudoku layout must have " + Sudoku.SIZE + " rows.");
+        }
+
+        this.template = new Sudoku.Cell[Sudoku.SIZE][Sudoku.SIZE];
+
+        // Keep track of which values in each row are not 'givens'.
+        for (int i = 0; i < Sudoku.SIZE; i++)
+        {
+            nonFixedValues.add(new ArrayList<Integer>(VALUES));
+        }
+
+        for (int i = 0; i < pattern.length; i++)
+        {
+            char[] rowPattern = pattern[i].toCharArray();
+            if (rowPattern.length != Sudoku.SIZE)
+            {
+                throw new IllegalArgumentException("Sudoku layout must have " + Sudoku.SIZE + " cells in each row.");
+            }
+            for (int j = 0; j < rowPattern.length; j++)
+            {
+                char c = rowPattern[j];
+                if (c >= '1' && c <= '9') // Cell is a 'given'.
+                {
+                    int value = c - '0'; // Convert char to in that it represents..
+                    template[i][j] = new Sudoku.Cell(value, true);
+                    List<Integer> rowValues = nonFixedValues.get(i);
+                    int index = Collections.binarySearch(rowValues, value);
+                    rowValues.remove(index);
+                }
+                else if (c != '.')
+                {
+                    throw new IllegalArgumentException("Unexpected character at (" + i + ", " + j + "): " + c);
+                }
+            }
+        }
+    }
+
+
+    /**
+     * {@inheritDoc}
+     * The generated potential solution is guaranteed to have no
+     * duplicates in any row but could have duplicates in a column or sub-grid.
+     */
+    public Sudoku generateRandomCandidate(Random rng)
+    {
+        // Clone the template as the basis for this grid.
+        Sudoku.Cell[][] rows = template.clone();
+        for (int i = 0; i < rows.length; i++)
+        {
+            rows[i] = template[i].clone();
+        }
+
+        // Fill-in the non-fixed cells.
+        for (int i = 0; i < rows.length; i++)
+        {
+            List<Integer> rowValues = nonFixedValues.get(i);
+            Collections.shuffle(rowValues);
+            int index = 0;
+            for (int j = 0; j < rows[i].length; j++)
+            {
+                if (rows[i][j] == null)
+                {
+                    rows[i][j] = new Sudoku.Cell(rowValues.get(index), false);
+                    ++index;
+                }
+            }
+        }
+        return new Sudoku(rows);
+    }
+}
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/sudoku/SudokuRowMutation.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/sudoku/SudokuRowMutation.java
new file mode 100644
index 0000000..029ae2b
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/sudoku/SudokuRowMutation.java
@@ -0,0 +1,206 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.sudoku;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Random;
+import org.uncommons.maths.number.ConstantGenerator;
+import org.uncommons.maths.number.NumberGenerator;
+import org.uncommons.watchmaker.framework.EvolutionaryOperator;
+
+/**
+ * Mutates rows in a potential Sudoku solution by manipulating the order
+ * of non-fixed cells in much the same way as the
+ * {@link org.uncommons.watchmaker.framework.operators.ListOrderMutation}
+ * operator does in the Travelling Salesman example.
+ * @author Daniel Dyer
+ */
+public class SudokuRowMutation implements EvolutionaryOperator<Sudoku>
+{
+    private final NumberGenerator<Integer> mutationCountVariable;
+    private final NumberGenerator<Integer> mutationAmountVariable;
+
+    // These look-up tables keep track of which values are fixed in which columns
+    // and sub-grids.  Because the values are fixed, they are the same for all
+    // potential solutions, so we cache the information here to minimise the amount
+    // of processing that needs to be done for each mutation.  There is no need to
+    // worry about rows since the mutation ensures that rows are always valid.
+    private final boolean[][] columnFixedValues = new boolean[Sudoku.SIZE][Sudoku.SIZE];
+    private final boolean[][] subGridFixedValues = new boolean[Sudoku.SIZE][Sudoku.SIZE];
+    private boolean cached = false;
+
+    /**
+     * Default is one mutation per candidate.
+     */
+    public SudokuRowMutation()
+    {
+        this(1, 1);
+    }
+
+    /**
+     * @param mutationCount The constant number of mutations
+     * to apply to each row in a Sudoku solution.
+     * @param mutationAmount The constant number of positions by
+     * which a list element will be displaced as a result of mutation.
+     */
+    public SudokuRowMutation(int mutationCount, int mutationAmount)
+    {
+        this(new ConstantGenerator<Integer>(mutationCount),
+             new ConstantGenerator<Integer>(mutationAmount));
+        if (mutationCount < 1)
+        {
+            throw new IllegalArgumentException("Mutation count must be at least 1.");
+        }
+        else if (mutationAmount < 1)
+        {
+            throw new IllegalArgumentException("Mutation amount must be at least 1.");
+        }
+    }
+
+
+    /**
+     * Typically the mutation count will be from a Poisson distribution.
+     * The mutation amount can be from any discrete probability distribution
+     * and can include negative values.
+     * @param mutationCount A random variable that provides a number
+     * of mutations that will be applied to each row in an individual.
+     * @param mutationAmount A random variable that provides a number
+     * of positions by which to displace an element when mutating.
+     */
+    public SudokuRowMutation(NumberGenerator<Integer> mutationCount,
+                             NumberGenerator<Integer> mutationAmount)
+    {
+        this.mutationCountVariable = mutationCount;
+        this.mutationAmountVariable = mutationAmount;
+    }
+
+
+    public List<Sudoku> apply(List<Sudoku> selectedCandidates, Random rng)
+    {
+        if (!cached)
+        {
+            buildCache(selectedCandidates.get(0));
+        }
+
+        List<Sudoku> mutatedCandidates = new ArrayList<Sudoku>(selectedCandidates.size());
+        for (Sudoku sudoku : selectedCandidates)
+        {
+            mutatedCandidates.add(mutate(sudoku, rng));
+        }
+        return mutatedCandidates;
+    }
+
+    
+    private Sudoku mutate(Sudoku sudoku, Random rng)
+    {
+        Sudoku.Cell[][] newRows = new Sudoku.Cell[Sudoku.SIZE][];
+        // Mutate each row in turn.
+        for (int i = 0; i < Sudoku.SIZE; i++)
+        {
+            newRows[i] = new Sudoku.Cell[Sudoku.SIZE];
+            System.arraycopy(sudoku.getRow(i), 0, newRows[i], 0, Sudoku.SIZE);
+        }
+
+        int mutationCount = Math.abs(mutationCountVariable.nextValue());
+        while (mutationCount > 0)
+        {
+            int row = rng.nextInt(Sudoku.SIZE);
+            int fromIndex = rng.nextInt(Sudoku.SIZE);
+            int mutationAmount = mutationAmountVariable.nextValue();
+            int toIndex = (fromIndex + mutationAmount) % Sudoku.SIZE;
+
+            // Make sure we're not trying to mutate a 'given'.
+            if (!newRows[row][fromIndex].isFixed()
+                && !newRows[row][toIndex].isFixed()
+                // ...or trying to introduce a duplicate of a given value.
+                && (!isIntroducingFixedConflict(sudoku, row, fromIndex, toIndex)
+                    || isRemovingFixedConflict(sudoku, row, fromIndex, toIndex)))
+            {
+                // Swap the randomly selected element with the one that is the
+                // specified displacement distance away.
+                Sudoku.Cell temp = newRows[row][fromIndex];
+                newRows[row][fromIndex] = newRows[row][toIndex];
+                newRows[row][toIndex] = temp;
+                --mutationCount;
+            }
+        }
+
+        return new Sudoku(newRows);
+    }
+
+
+    private void buildCache(Sudoku sudoku)
+    {
+        for (int row = 0; row < Sudoku.SIZE; row++)
+        {
+            for (int column = 0; column < Sudoku.SIZE; column++)
+            {
+                if (sudoku.isFixed(row, column))
+                {
+                    columnFixedValues[column][sudoku.getValue(row, column) - 1] = true;
+                    subGridFixedValues[convertToSubGrid(row, column)][sudoku.getValue(row, column) - 1] = true;
+                }
+            }
+        }
+        cached = true;
+    }
+
+
+    /**
+     * Checks whether the proposed mutation would introduce a duplicate of a fixed value
+     * into a column or sub-grid.
+     */
+    private boolean isIntroducingFixedConflict(Sudoku sudoku,
+                                               int row,
+                                               int fromIndex,
+                                               int toIndex)
+    {
+        return columnFixedValues[fromIndex][sudoku.getValue(row, toIndex) - 1]
+               || columnFixedValues[toIndex][sudoku.getValue(row, fromIndex) - 1]
+               || subGridFixedValues[convertToSubGrid(row, fromIndex)][sudoku.getValue(row, toIndex) - 1]
+               || subGridFixedValues[convertToSubGrid(row, toIndex)][sudoku.getValue(row, fromIndex) - 1];
+    }
+
+
+    /**
+     * Checks whether the proposed mutation would remove a duplicate of a fixed value
+     * from a column or sub-grid.
+     */
+    private boolean isRemovingFixedConflict(Sudoku sudoku,
+                                            int row,
+                                            int fromIndex,
+                                            int toIndex)
+    {
+        return columnFixedValues[fromIndex][sudoku.getValue(row, fromIndex) - 1]
+               || columnFixedValues[toIndex][sudoku.getValue(row, toIndex) - 1]
+               || subGridFixedValues[convertToSubGrid(row, fromIndex)][sudoku.getValue(row, fromIndex) - 1]
+               || subGridFixedValues[convertToSubGrid(row, toIndex)][sudoku.getValue(row, toIndex) - 1];
+    }
+
+
+
+    /**
+     * Returns the index of the sub-grid that the specified cells belongs to.
+     * @return A number between 0 (top left) and 8 (bottom right).
+     */
+    private int convertToSubGrid(int row, int column)
+    {
+        int band = row / 3;
+        int stack = column / 3;
+        return band * 3 + stack;
+    }
+}
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/sudoku/SudokuTableModel.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/sudoku/SudokuTableModel.java
new file mode 100644
index 0000000..0249f7f
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/sudoku/SudokuTableModel.java
@@ -0,0 +1,156 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.sudoku;
+
+import javax.swing.table.AbstractTableModel;
+
+/**
+ * {@link javax.swing.table.TableModel} for displaying a Sudoku
+ * grid in a {@link javax.swing.JTable}.
+ * @author Daniel Dyer
+ */
+class SudokuTableModel extends AbstractTableModel
+{
+    // In puzzle mode, the user can edit the given cells and all other
+    // cells are blank.  In solution mode, all cells have values and are
+    // uneditable.
+    private boolean puzzleMode = true;
+
+    // Solution mode data.
+    private Sudoku sudoku;
+
+    // Puzzle mode data.
+    private final Character[][] cells = new Character[Sudoku.SIZE][Sudoku.SIZE];
+
+
+    /**
+     * Sets the Sudoku grid represented by this table model.
+     */
+    public void setSudoku(Sudoku sudoku)
+    {
+        this.sudoku = sudoku;
+        puzzleMode = false;
+        fireTableRowsUpdated(0, getRowCount() - 1);
+    }
+
+
+    /**
+     * @return The Sudoku grid represented by this table model.
+     */
+    public Sudoku getSudoku()
+    {
+        return sudoku;
+    }
+
+    
+    public int getRowCount()
+    {
+        return Sudoku.SIZE;
+    }
+
+
+    public int getColumnCount()
+    {
+        return Sudoku.SIZE;
+    }
+
+
+    public Object getValueAt(int row, int column)
+    {
+        if (puzzleMode)
+        {
+            return cells[row][column];
+        }
+        else
+        {
+            return sudoku == null ? null : sudoku.getValue(row, column);
+        }
+    }
+
+
+    @Override
+    public boolean isCellEditable(int row, int column)
+    {
+        return puzzleMode;
+    }
+
+
+    @Override
+    public void setValueAt(Object object, int row, int column)
+    {
+        Character value = (Character) object;
+        if (!(value == null || (value >= '1' && value <= '9')))
+        {
+            throw new IllegalArgumentException("Invalid character: " + value);
+        }
+        cells[row][column] = value;
+        fireTableCellUpdated(row, column);
+    }
+
+
+    /**
+     * Sets all cells at once using the same patterns as supported by
+     * {@link SudokuFactory}.
+     * @param pattern A String representation of a Sudoku puzzle.  Each element
+     * in the array represents a single row.  There are 9 elements and each has 9
+     * characters, one per cell.  Number cells are represented by the characters
+     * '0' to '9' and blank cells are represented by dots.
+     */
+    public void setPattern(String[] pattern)
+    {
+        if (pattern.length != Sudoku.SIZE)
+        {
+            throw new IllegalArgumentException("Pattern must have " + Sudoku.SIZE + " rows.");
+        }
+        for (int row = 0; row < pattern.length; row++)
+        {
+            String patternRow = pattern[row];
+            if (patternRow.length() != Sudoku.SIZE)
+            {
+                throw new IllegalArgumentException("Row must have " + Sudoku.SIZE + " columns.");
+            }
+            for (int column = 0; column < patternRow.toCharArray().length; column++)
+            {
+                char c = patternRow.toCharArray()[column];
+                cells[row][column] = c == '.' ? null : c;
+            }
+        }
+        sudoku = null;
+        puzzleMode = true;
+        fireTableRowsUpdated(0, getRowCount() - 1);
+    }
+
+
+    /**
+     * @return A Sudoku puzzle in the pattern format used by {@link SudokuFactory}.
+     */
+    public String[] getPattern()
+    {
+        String[] pattern = new String[Sudoku.SIZE];
+        for (int i = 0; i < cells.length; i++)
+        {
+            Character[] row = cells[i];
+            StringBuilder rowString = new StringBuilder();
+            for (Character c : row)
+            {
+                rowString.append(c == null ? '.' : c);
+            }
+            pattern[i] = rowString.toString();
+        }
+        return pattern;
+    }
+
+}
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/sudoku/SudokuVerticalCrossover.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/sudoku/SudokuVerticalCrossover.java
new file mode 100644
index 0000000..e5c790f
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/sudoku/SudokuVerticalCrossover.java
@@ -0,0 +1,105 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.sudoku;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Random;
+import org.uncommons.maths.number.NumberGenerator;
+import org.uncommons.watchmaker.framework.operators.AbstractCrossover;
+
+/**
+ * Performs cross-over between Sudoku grids by re-combining rows from parents
+ * to form new offspring.  Rows are copied intact, only columns are disrupted
+ * by this cross-over.
+ * @author Daniel Dyer
+ */
+public class SudokuVerticalCrossover extends AbstractCrossover<Sudoku>
+{
+    /**
+     * Single-point cross-over.
+     */
+    public SudokuVerticalCrossover()
+    {
+        this(1);
+    }
+
+
+    /**
+     * Multiple-point cross-over (fixed number of points).
+     * @param crossoverPoints The fixed number of cross-overs applied to each
+     * pair of parents.
+     */
+    public SudokuVerticalCrossover(int crossoverPoints)
+    {
+        super(crossoverPoints);
+    }
+
+
+    /**
+     * Multiple-point cross-over (variable number of points).
+     * @param crossoverPointsVariable Provides the (possibly variable) number of
+     * cross-overs applied to each pair of parents.
+     */
+    public SudokuVerticalCrossover(NumberGenerator<Integer> crossoverPointsVariable)
+    {
+        super(crossoverPointsVariable);
+    }
+
+
+    /**
+     * Applies cross-over to a pair of parents.  Cross-over is performed vertically
+     * (each offspring consists of some rows from {@literal parent1} and some rows
+     * from {@literal parent2}).
+     * @param parent1 The first parent.
+     * @param parent2 The second parent.
+     * @param numberOfCrossoverPoints The number of cross-overs to perform.
+     * @param rng The RNG used to select the cross-over points.
+     * @return A list containing a pair of offspring.
+     */
+    @Override
+    protected List<Sudoku> mate(Sudoku parent1,
+                                Sudoku parent2,
+                                int numberOfCrossoverPoints,
+                                Random rng)
+    {
+        Sudoku.Cell[][] offspring1 = new Sudoku.Cell[Sudoku.SIZE][];
+        Sudoku.Cell[][] offspring2 = new Sudoku.Cell[Sudoku.SIZE][];
+        for (int i = 0; i < Sudoku.SIZE; i++)
+        {
+            offspring1[i] = parent1.getRow(i);
+            offspring2[i] = parent2.getRow(i);
+        }
+        
+        // Apply as many cross-overs as required.
+        Sudoku.Cell[][] temp = new Sudoku.Cell[Sudoku.SIZE][];
+        for (int i = 0; i < numberOfCrossoverPoints; i++)
+        {
+            // Cross-over index is always greater than zero and less than
+            // the length of the parent so that we always pick a point that
+            // will result in a meaningful cross-over.
+            int crossoverIndex = (1 + rng.nextInt(Sudoku.SIZE - 1));
+            System.arraycopy(offspring1, 0, temp, 0, crossoverIndex);
+            System.arraycopy(offspring2, 0, offspring1, 0, crossoverIndex);
+            System.arraycopy(temp, 0, offspring2, 0, crossoverIndex);
+        }
+
+        List<Sudoku> result = new ArrayList<Sudoku>(2);
+        result.add(new Sudoku(offspring1));
+        result.add(new Sudoku(offspring2));
+        return result;
+    }
+}
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/sudoku/SudokuView.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/sudoku/SudokuView.java
new file mode 100644
index 0000000..1f8f269
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/sudoku/SudokuView.java
@@ -0,0 +1,76 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.sudoku;
+
+import java.awt.BorderLayout;
+import java.awt.Color;
+import javax.swing.BorderFactory;
+import javax.swing.DefaultCellEditor;
+import javax.swing.JComboBox;
+import javax.swing.JPanel;
+import javax.swing.JTable;
+import javax.swing.table.TableCellEditor;
+import javax.swing.table.TableCellRenderer;
+import javax.swing.table.TableColumn;
+import javax.swing.table.TableColumnModel;
+
+/**
+ * A component for displaying Sudoku puzzles and solutions.
+ * @author Daniel Dyer
+ */
+class SudokuView extends JPanel
+{
+    private final SudokuTableModel sudokuTableModel = new SudokuTableModel();
+
+    SudokuView()
+    {
+        super(new BorderLayout());
+        JTable sudokuTable = new JTable(sudokuTableModel);
+        sudokuTable.setRowHeight(40);
+        sudokuTable.setGridColor(Color.GRAY);
+        sudokuTable.setShowGrid(true);
+        TableColumnModel columnModel = sudokuTable.getColumnModel();
+        TableCellRenderer renderer = new SudokuCellRenderer();
+        JComboBox valueCombo = new JComboBox(new Object[]{null, '1', '2', '3', '4', '5', '6', '7', '8', '9'});
+        TableCellEditor editor = new DefaultCellEditor(valueCombo);
+        for (int i = 0; i < columnModel.getColumnCount(); i++)
+        {
+            TableColumn column = columnModel.getColumn(i);
+            column.setCellRenderer(renderer);
+            column.setCellEditor(editor);
+        }
+        add(sudokuTable, BorderLayout.CENTER);
+        setBorder(BorderFactory.createTitledBorder("Puzzle/Solution"));
+    }
+
+
+    public void setSolution(Sudoku sudoku)
+    {
+        sudokuTableModel.setSudoku(sudoku);
+    }
+
+
+    public void setPuzzle(String[] pattern)
+    {
+        sudokuTableModel.setPattern(pattern);
+    }
+
+
+    public String[] getPuzzle()
+    {
+        return sudokuTableModel.getPattern();
+    }
+}
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/sudoku/package-info.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/sudoku/package-info.java
new file mode 100644
index 0000000..bd69653
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/sudoku/package-info.java
@@ -0,0 +1,20 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+/**
+ * An evolutionary Sudoku solver.
+ * @author Daniel Dyer
+ */
+package org.uncommons.watchmaker.examples.sudoku;
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/travellingsalesman/BruteForceTravellingSalesman.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/travellingsalesman/BruteForceTravellingSalesman.java
new file mode 100644
index 0000000..312e6d4
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/travellingsalesman/BruteForceTravellingSalesman.java
@@ -0,0 +1,107 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.travellingsalesman;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.Iterator;
+import java.util.List;
+import org.uncommons.maths.combinatorics.PermutationGenerator;
+import org.uncommons.watchmaker.framework.FitnessEvaluator;
+
+/**
+ * Naive brute-force solution to the travelling salesman problem. It would take about
+ * a day and a half to brute-force the 15-city travelling salesman problem on a home
+ * computer using this implementation.  However, this is a not the best possible
+ * implementation that is guaranteed to find a the shortest route (for example there
+ * is no branch-and-bound optimisation).
+ * @author Daniel Dyer
+ */
+public class BruteForceTravellingSalesman implements TravellingSalesmanStrategy
+{
+    private final DistanceLookup distances;
+
+
+    /**
+     * @param distances Information about the distances between cities.
+     */
+    public BruteForceTravellingSalesman(DistanceLookup distances)
+    {
+        this.distances = distances;
+    }
+
+    
+    /**
+     * {@inheritDoc}
+     */
+    public String getDescription()
+    {
+        return "Brute Force";
+    }
+
+    
+    /**
+     * To reduce the search space we will only consider routes that start
+     * and end at one city (whichever is first in the collection).  All other
+     * possible routes are equivalent to one of these routes since start city
+     * is irrelevant in determining the shortest cycle.
+     * @param cities The list of destinations, each of which must be visited
+     * once.
+     * @param progressListener Call-back for receiving the status of the
+     * algorithm as it progresses.  May be null.
+     * @return The shortest route that visits each of the specified cities once.
+     */
+    public List<String> calculateShortestRoute(Collection<String> cities,
+                                               ProgressListener progressListener)
+    {
+        Iterator<String> iterator = cities.iterator();
+        String startCity = iterator.next();
+        Collection<String> destinations = new ArrayList<String>(cities.size() - 1);
+        while (iterator.hasNext())
+        {
+            destinations.add(iterator.next());
+        }
+
+        FitnessEvaluator<List<String>> evaluator = new RouteEvaluator(distances);
+        PermutationGenerator<String> generator = new PermutationGenerator<String>(destinations);
+        long totalPermutations = generator.getTotalPermutations();
+        long count = 0;
+        List<String> shortestRoute = null;
+        double shortestDistance = Double.POSITIVE_INFINITY;
+        List<String> currentRoute = new ArrayList<String>(cities.size());
+        while (generator.hasMore())
+        {
+            List<String> route = generator.nextPermutationAsList(currentRoute);
+            route.add(0, startCity);
+            double distance = evaluator.getFitness(route, null);
+            if (distance < shortestDistance)
+            {
+                shortestDistance = distance;
+                shortestRoute = new ArrayList<String>(route);
+            }
+            ++count;
+            if (count % 1000 == 0 && progressListener != null)
+            {
+                progressListener.updateProgress(((double) count) / totalPermutations * 100);
+            }
+        }
+        if (progressListener != null)
+        {
+            progressListener.updateProgress(100); // Finished.
+        }
+        return shortestRoute;
+    }
+}
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/travellingsalesman/DistanceLookup.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/travellingsalesman/DistanceLookup.java
new file mode 100644
index 0000000..9013d75
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/travellingsalesman/DistanceLookup.java
@@ -0,0 +1,39 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.travellingsalesman;
+
+import java.util.List;
+
+/**
+ * Strategy interface for providing distances between cities in the
+ * Travelling Salesman problem.
+ * @author Daniel Dyer
+ */
+public interface DistanceLookup
+{
+    /**
+     * @return The list of cities that this object knows about.
+     */
+    List<String> getKnownCities();
+
+    /**
+     * Looks-up the distance between two cities.
+     * @param startingCity The city to start from.
+     * @param destinationCity The city to end in.
+     * @return The distance (in kilometres) between the two cities.
+     */
+    int getDistance(String startingCity, String destinationCity);
+}
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/travellingsalesman/EuropeanDistanceLookup.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/travellingsalesman/EuropeanDistanceLookup.java
new file mode 100644
index 0000000..547347f
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/travellingsalesman/EuropeanDistanceLookup.java
@@ -0,0 +1,326 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.travellingsalesman;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+/**
+ * This class contains data about cities in Europe and the distances
+ * between them.
+ * @author Daniel Dyer
+ */
+public final class EuropeanDistanceLookup implements DistanceLookup
+{
+    private static final Map<String, Map<String, Integer>> DISTANCES = new HashMap<String, Map<String, Integer>>(15);
+    static
+    {
+        // Distances are in km as the crow flies (from http://www.indo.com/distance/)
+
+        Map<String, Integer> amsterdam = new HashMap<String, Integer>(20);
+        amsterdam.put("Amsterdam", 0);
+        amsterdam.put("Athens", 2162);
+        amsterdam.put("Berlin", 576);
+        amsterdam.put("Brussels", 171);
+        amsterdam.put("Copenhagen", 622);
+        amsterdam.put("Dublin", 757);
+        amsterdam.put("Helsinki", 1506);
+        amsterdam.put("Lisbon", 1861);
+        amsterdam.put("London", 356);
+        amsterdam.put("Luxembourg", 318);
+        amsterdam.put("Madrid", 1477);
+        amsterdam.put("Paris", 429);
+        amsterdam.put("Rome", 1304);
+        amsterdam.put("Stockholm", 1132);
+        amsterdam.put("Vienna", 938);
+        DISTANCES.put("Amsterdam", amsterdam);
+
+        Map<String, Integer> athens = new HashMap<String, Integer>(20);
+        athens.put("Amsterdam", 2162);
+        athens.put("Athens", 0);
+        athens.put("Berlin", 1801);
+        athens.put("Brussels", 2089);
+        athens.put("Copenhagen", 2140);
+        athens.put("Dublin", 2860);
+        athens.put("Helsinki", 2464);
+        athens.put("Lisbon", 2854);
+        athens.put("London", 2391);
+        athens.put("Luxembourg", 1901);
+        athens.put("Madrid", 2374);
+        athens.put("Paris", 2097);
+        athens.put("Rome", 1040);
+        athens.put("Stockholm", 2410);
+        athens.put("Vienna", 1280);
+        DISTANCES.put("Athens", athens);
+
+        Map<String, Integer> berlin = new HashMap<String, Integer>(20);
+        berlin.put("Amsterdam", 576);
+        berlin.put("Athens", 1801);
+        berlin.put("Berlin", 0);
+        berlin.put("Brussels", 648);
+        berlin.put("Copenhagen", 361);
+        berlin.put("Dublin", 1315);
+        berlin.put("Helsinki", 1108);
+        berlin.put("Lisbon", 2310);
+        berlin.put("London", 929);
+        berlin.put("Luxembourg", 595);
+        berlin.put("Madrid", 1866);
+        berlin.put("Paris", 877);
+        berlin.put("Rome", 1185);
+        berlin.put("Stockholm", 818);
+        berlin.put("Vienna", 525);
+        DISTANCES.put("Berlin", berlin);
+
+        Map<String, Integer> brussels = new HashMap<String, Integer>(20);
+        brussels.put("Amsterdam", 171);
+        brussels.put("Athens", 2089);
+        brussels.put("Berlin", 648);
+        brussels.put("Brussels", 0);
+        brussels.put("Copenhagen", 764);
+        brussels.put("Dublin", 780);
+        brussels.put("Helsinki", 1649);
+        brussels.put("Lisbon", 1713);
+        brussels.put("London", 321);
+        brussels.put("Luxembourg", 190);
+        brussels.put("Madrid", 1315);
+        brussels.put("Paris", 266);
+        brussels.put("Rome", 1182);
+        brussels.put("Stockholm", 1284);
+        brussels.put("Vienna", 917);
+        DISTANCES.put("Brussels", brussels);
+
+        Map<String, Integer> copenhagen = new HashMap<String, Integer>(20);
+        copenhagen.put("Amsterdam", 622);
+        copenhagen.put("Athens", 2140);
+        copenhagen.put("Berlin", 361);
+        copenhagen.put("Brussels", 764);
+        copenhagen.put("Copenhagen", 0);
+        copenhagen.put("Dublin", 1232);
+        copenhagen.put("Helsinki", 885);
+        copenhagen.put("Lisbon", 2477);
+        copenhagen.put("London", 953);
+        copenhagen.put("Luxembourg", 799);
+        copenhagen.put("Madrid", 2071);
+        copenhagen.put("Paris", 1028);
+        copenhagen.put("Rome", 1540);
+        copenhagen.put("Stockholm", 526);
+        copenhagen.put("Vienna", 876);
+        DISTANCES.put("Copenhagen", copenhagen);
+
+        Map<String, Integer> dublin = new HashMap<String, Integer>(20);
+        dublin.put("Amsterdam", 757);
+        dublin.put("Athens", 2860);
+        dublin.put("Berlin", 1315);
+        dublin.put("Brussels", 780);
+        dublin.put("Copenhagen", 1232);
+        dublin.put("Dublin", 0);
+        dublin.put("Helsinki", 2021);
+        dublin.put("Lisbon", 1652);
+        dublin.put("London", 469);
+        dublin.put("Luxembourg", 961);
+        dublin.put("Madrid", 1458);
+        dublin.put("Paris", 787);
+        dublin.put("Rome", 1903);
+        dublin.put("Stockholm", 1625);
+        dublin.put("Vienna", 1687);
+        DISTANCES.put("Dublin", dublin);
+
+        Map<String, Integer> helsinki = new HashMap<String, Integer>(20);
+        helsinki.put("Amsterdam", 1506);
+        helsinki.put("Athens", 2464);
+        helsinki.put("Berlin", 1108);
+        helsinki.put("Brussels", 1649);
+        helsinki.put("Copenhagen", 885);
+        helsinki.put("Dublin", 2021);
+        helsinki.put("Helsinki", 0);
+        helsinki.put("Lisbon", 3362);
+        helsinki.put("London", 1823);
+        helsinki.put("Luxembourg", 1667);
+        helsinki.put("Madrid", 2949);
+        helsinki.put("Paris", 1912);
+        helsinki.put("Rome", 2202);
+        helsinki.put("Stockholm", 396);
+        helsinki.put("Vienna", 1439);
+        DISTANCES.put("Helsinki", helsinki);
+
+        Map<String, Integer> lisbon = new HashMap<String, Integer>(20);
+        lisbon.put("Amsterdam", 1861);
+        lisbon.put("Athens", 2854);
+        lisbon.put("Berlin", 2310);
+        lisbon.put("Brussels", 1713);
+        lisbon.put("Copenhagen", 2477);
+        lisbon.put("Dublin", 1652);
+        lisbon.put("Helsinki", 3362);
+        lisbon.put("Lisbon", 0);
+        lisbon.put("London", 1585);
+        lisbon.put("Luxembourg", 1716);
+        lisbon.put("Madrid", 501);
+        lisbon.put("Paris", 1452);
+        lisbon.put("Rome", 1873);
+        lisbon.put("Stockholm", 2993);
+        lisbon.put("Vienna", 2300);
+        DISTANCES.put("Lisbon", lisbon);
+
+        Map<String, Integer> london = new HashMap<String, Integer>(20);
+        london.put("Amsterdam", 356);
+        london.put("Athens", 2391);
+        london.put("Berlin", 929);
+        london.put("Brussels", 321);
+        london.put("Copenhagen", 953);
+        london.put("Dublin", 469);
+        london.put("Helsinki", 1823);
+        london.put("Lisbon", 1585);
+        london.put("London", 0);
+        london.put("Luxembourg", 494);
+        london.put("Madrid", 1261);
+        london.put("Paris", 343);
+        london.put("Rome", 1444);
+        london.put("Stockholm", 1436);
+        london.put("Vienna", 1237);
+        DISTANCES.put("London", london);
+
+        Map<String, Integer> luxembourg = new HashMap<String, Integer>(20);
+        luxembourg.put("Amsterdam", 318);
+        luxembourg.put("Athens", 1901);
+        luxembourg.put("Berlin", 595);
+        luxembourg.put("Brussels", 190);
+        luxembourg.put("Copenhagen", 799);
+        luxembourg.put("Dublin", 961);
+        luxembourg.put("Helsinki", 1667);
+        luxembourg.put("Lisbon", 1716);
+        luxembourg.put("London", 494);
+        luxembourg.put("Luxembourg", 0);
+        luxembourg.put("Madrid", 1282);
+        luxembourg.put("Paris", 294);
+        luxembourg.put("Rome", 995);
+        luxembourg.put("Stockholm", 1325);
+        luxembourg.put("Vienna", 761);
+        DISTANCES.put("Luxembourg", luxembourg);
+
+        Map<String, Integer> madrid = new HashMap<String, Integer>(20);
+        madrid.put("Amsterdam", 1477);
+        madrid.put("Athens", 2374);
+        madrid.put("Berlin", 1866);
+        madrid.put("Brussels", 1315);
+        madrid.put("Copenhagen", 2071);
+        madrid.put("Dublin", 1458);
+        madrid.put("Helsinki", 2949);
+        madrid.put("Lisbon", 501);
+        madrid.put("London", 1261);
+        madrid.put("Luxembourg", 1282);
+        madrid.put("Madrid", 0);
+        madrid.put("Paris", 1050);
+        madrid.put("Rome", 1377);
+        madrid.put("Stockholm", 2596);
+        madrid.put("Vienna", 1812);
+        DISTANCES.put("Madrid", madrid);
+
+        Map<String, Integer> paris = new HashMap<String, Integer>(20);
+        paris.put("Amsterdam", 429);
+        paris.put("Athens", 2097);
+        paris.put("Berlin", 877);
+        paris.put("Brussels", 266);
+        paris.put("Copenhagen", 1028);
+        paris.put("Dublin", 787);
+        paris.put("Helsinki", 1912);
+        paris.put("Lisbon", 1452);
+        paris.put("London", 343);
+        paris.put("Luxembourg", 294);
+        paris.put("Madrid", 1050);
+        paris.put("Paris", 0);
+        paris.put("Rome", 1117);
+        paris.put("Stockholm", 1549);
+        paris.put("Vienna", 1037);
+        DISTANCES.put("Paris", paris);
+
+        Map<String, Integer> rome = new HashMap<String, Integer>(20);
+        rome.put("Amsterdam", 1304);
+        rome.put("Athens", 1040);
+        rome.put("Berlin", 1185);
+        rome.put("Brussels", 1182);
+        rome.put("Copenhagen", 1540);
+        rome.put("Dublin", 1903);
+        rome.put("Helsinki", 2202);
+        rome.put("Lisbon", 1873);
+        rome.put("London", 1444);
+        rome.put("Luxembourg", 995);
+        rome.put("Madrid", 1377);
+        rome.put("Paris", 1117);
+        rome.put("Rome", 0);
+        rome.put("Stockholm", 1984);
+        rome.put("Vienna", 765);
+        DISTANCES.put("Rome", rome);
+
+        Map<String, Integer> stockholm = new HashMap<String, Integer>(20);
+        stockholm.put("Amsterdam", 1132);
+        stockholm.put("Athens", 2410);
+        stockholm.put("Berlin", 818);
+        stockholm.put("Brussels", 1284);
+        stockholm.put("Copenhagen", 526);
+        stockholm.put("Dublin", 1625);
+        stockholm.put("Helsinki", 396);
+        stockholm.put("Lisbon", 2993);
+        stockholm.put("London", 1436);
+        stockholm.put("Luxembourg", 1325);
+        stockholm.put("Madrid", 2596);
+        stockholm.put("Paris", 1549);
+        stockholm.put("Rome", 1984);
+        stockholm.put("Stockholm", 0);
+        stockholm.put("Vienna", 1247);
+        DISTANCES.put("Stockholm", stockholm);
+
+        Map<String, Integer> vienna = new HashMap<String, Integer>(20);
+        vienna.put("Amsterdam", 938);
+        vienna.put("Athens", 1280);
+        vienna.put("Berlin", 525);
+        vienna.put("Brussels", 917);
+        vienna.put("Copenhagen", 876);
+        vienna.put("Dublin", 1687);
+        vienna.put("Helsinki", 1439);
+        vienna.put("Lisbon", 2300);
+        vienna.put("London", 1237);
+        vienna.put("Luxembourg", 761);
+        vienna.put("Madrid", 1812);
+        vienna.put("Paris", 1037);
+        vienna.put("Rome", 765);
+        vienna.put("Stockholm", 1247);
+        vienna.put("Vienna", 0);
+        DISTANCES.put("Vienna", vienna);
+    }
+
+
+    /**
+     * {@inheritDoc}
+     */
+    public List<String> getKnownCities()
+    {
+        List<String> cities = new ArrayList<String>(DISTANCES.keySet());
+        Collections.sort(cities);
+        return cities;
+    }
+
+
+    /**
+     * {@inheritDoc}
+     */
+    public int getDistance(String startingCity, String destinationCity)
+    {
+        return DISTANCES.get(startingCity).get(destinationCity);
+    }
+}
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/travellingsalesman/EvolutionPanel.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/travellingsalesman/EvolutionPanel.java
new file mode 100644
index 0000000..82089d5
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/travellingsalesman/EvolutionPanel.java
@@ -0,0 +1,119 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.travellingsalesman;
+
+import java.awt.FlowLayout;
+import java.util.List;
+import javax.swing.JCheckBox;
+import javax.swing.JLabel;
+import javax.swing.JPanel;
+import javax.swing.JSpinner;
+import javax.swing.SpinnerNumberModel;
+import javax.swing.SpringLayout;
+import org.uncommons.maths.random.Probability;
+import org.uncommons.swing.SpringUtilities;
+import org.uncommons.watchmaker.framework.SelectionStrategy;
+import org.uncommons.watchmaker.swing.SelectionStrategyControl;
+
+/**
+ * Controls for configuring an {@link EvolutionaryTravellingSalesman} object.
+ * @author Daniel Dyer
+ */
+final class EvolutionPanel extends JPanel
+{
+    private final JLabel populationLabel;
+    private final JSpinner populationSpinner;
+    private final JLabel elitismLabel;
+    private final JSpinner elitismSpinner;
+    private final JLabel generationsLabel;
+    private final JSpinner generationsSpinner;
+    private final JLabel selectionLabel;
+    private final SelectionStrategyControl<List<String>> selectionControl;
+    private final JCheckBox crossoverCheckbox;
+    private final JCheckBox mutationCheckbox;
+    private final DistanceLookup distances;
+
+    EvolutionPanel(DistanceLookup distances)
+    {
+        super(new FlowLayout(FlowLayout.LEFT, 0, 0));
+        this.distances = distances;
+        JPanel innerPanel = new JPanel(new SpringLayout());
+
+        populationLabel = new JLabel("Population Size: ");
+        populationSpinner = new JSpinner(new SpinnerNumberModel(300, 2, 10000, 1));
+        populationLabel.setLabelFor(populationSpinner);
+        innerPanel.add(populationLabel);
+        innerPanel.add(populationSpinner);
+
+        elitismLabel = new JLabel("Elitism: ");
+        elitismSpinner = new JSpinner(new SpinnerNumberModel(3, 0, 10000, 1));
+        elitismLabel.setLabelFor(elitismSpinner);
+        innerPanel.add(elitismLabel);
+        innerPanel.add(elitismSpinner);
+
+        generationsLabel = new JLabel("Number of Generations: ");
+        generationsSpinner = new JSpinner(new SpinnerNumberModel(100, 1, 10000, 1));
+        generationsLabel.setLabelFor(generationsSpinner);
+        innerPanel.add(generationsLabel);
+        innerPanel.add(generationsSpinner);
+
+        selectionLabel = new JLabel("Selection Strategy: ");
+        List<SelectionStrategy<? super List<String>>> strategies
+            = SelectionStrategyControl.createDefaultOptions(new Probability(0.95d), 0.5d);
+        this.selectionControl = new SelectionStrategyControl<List<String>>(strategies);
+        innerPanel.add(selectionLabel);
+        selectionControl.getControl().setSelectedIndex(selectionControl.getControl().getItemCount() - 1);
+        innerPanel.add(selectionControl.getControl());
+
+        crossoverCheckbox = new JCheckBox("Cross-over", true);
+        mutationCheckbox = new JCheckBox("Mutation", true);
+
+        innerPanel.add(crossoverCheckbox);
+        innerPanel.add(mutationCheckbox);
+
+        SpringUtilities.makeCompactGrid(innerPanel, 5, 2, 30, 6, 6, 6);
+        add(innerPanel);
+    }
+
+
+    @Override
+    public void setEnabled(boolean b)
+    {
+        populationLabel.setEnabled(b);
+        populationSpinner.setEnabled(b);
+        elitismLabel.setEnabled(b);
+        elitismSpinner.setEnabled(b);
+        generationsLabel.setEnabled(b);
+        generationsSpinner.setEnabled(b);
+        selectionLabel.setEnabled(b);
+        selectionControl.getControl().setEnabled(b);
+        crossoverCheckbox.setEnabled(b);
+        mutationCheckbox.setEnabled(b);
+        super.setEnabled(b);
+    }
+
+
+    public TravellingSalesmanStrategy getStrategy()
+    {
+        return new EvolutionaryTravellingSalesman(distances,
+                                                  selectionControl.getSelectionStrategy(),
+                                                  (Integer) populationSpinner.getValue(),
+                                                  (Integer) elitismSpinner.getValue(),
+                                                  (Integer) generationsSpinner.getValue(),
+                                                  crossoverCheckbox.isSelected(),
+                                                  mutationCheckbox.isSelected());
+    }
+}
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/travellingsalesman/EvolutionaryTravellingSalesman.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/travellingsalesman/EvolutionaryTravellingSalesman.java
new file mode 100644
index 0000000..6814101
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/travellingsalesman/EvolutionaryTravellingSalesman.java
@@ -0,0 +1,152 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.travellingsalesman;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Random;
+import org.uncommons.maths.random.MersenneTwisterRNG;
+import org.uncommons.maths.random.PoissonGenerator;
+import org.uncommons.watchmaker.framework.CandidateFactory;
+import org.uncommons.watchmaker.framework.EvolutionEngine;
+import org.uncommons.watchmaker.framework.EvolutionObserver;
+import org.uncommons.watchmaker.framework.EvolutionaryOperator;
+import org.uncommons.watchmaker.framework.GenerationalEvolutionEngine;
+import org.uncommons.watchmaker.framework.PopulationData;
+import org.uncommons.watchmaker.framework.SelectionStrategy;
+import org.uncommons.watchmaker.framework.factories.ListPermutationFactory;
+import org.uncommons.watchmaker.framework.operators.EvolutionPipeline;
+import org.uncommons.watchmaker.framework.operators.ListOrderCrossover;
+import org.uncommons.watchmaker.framework.operators.ListOrderMutation;
+import org.uncommons.watchmaker.framework.termination.GenerationCount;
+
+/**
+ * Evolutionary algorithm for finding (approximate) solutions to the
+ * travelling salesman problem.
+ * @author Daniel Dyer
+ */
+public class EvolutionaryTravellingSalesman implements TravellingSalesmanStrategy
+{
+    private final DistanceLookup distances;
+    private final SelectionStrategy<? super List<String>> selectionStrategy;
+    private final int populationSize;
+    private final int eliteCount;
+    private final int generationCount;
+    private final boolean crossover;
+    private final boolean mutation;
+
+    /**
+     * Creates an evolutionary Travelling Salesman solver with the
+     * specified configuration.
+     * @param distances Information about the distances between cities.
+     * @param selectionStrategy The selection implementation to use for
+     * the evolutionary algorithm.
+     * @param populationSize The number of candidates in the population
+     * of evolved routes.
+     * @param eliteCount The number of candidates to preserve via elitism
+     * at each generation.
+     * @param generationCount The number of iterations of evolution to perform.
+     * @param crossover Whether or not to use a cross-over operator in the evolution.
+     * @param mutation Whether or not to use a mutation operator in the evolution.
+     */
+    public EvolutionaryTravellingSalesman(DistanceLookup distances,
+                                          SelectionStrategy<? super List<String>> selectionStrategy,
+                                          int populationSize,
+                                          int eliteCount,
+                                          int generationCount,
+                                          boolean crossover,
+                                          boolean mutation)
+    {
+        if (!crossover && !mutation)
+        {
+            throw new IllegalArgumentException("At least one of cross-over or mutation must be selected.");
+        }
+        this.distances = distances;
+        this.selectionStrategy = selectionStrategy;
+        this.populationSize = populationSize;
+        this.eliteCount = eliteCount;
+        this.generationCount = generationCount;
+        this.crossover = crossover;
+        this.mutation = mutation;
+    }
+
+
+    /**
+     * {@inheritDoc}
+     */
+    public String getDescription()
+    {
+        String selectionName = selectionStrategy.toString();
+        return "Evolution (pop: " + populationSize + ", gen: " + generationCount
+                + ", elite: " + eliteCount + ", " + selectionName + ")";
+    }
+
+
+    /**
+     * Calculates the shortest route using a generational evolutionary
+     * algorithm with a single ordered mutation operator and truncation
+     * selection.
+     * @param cities The list of destinations, each of which must be visited
+     * once.
+     * @param progressListener Call-back for receiving the status of the
+     * algorithm as it progresses.
+     * @return The (approximate) shortest route that visits each of the
+     * specified cities once.
+     */
+    public List<String> calculateShortestRoute(Collection<String> cities,
+                                               final ProgressListener progressListener)
+    {
+        Random rng = new MersenneTwisterRNG();
+
+        // Set-up evolution pipeline (cross-over followed by mutation).
+        List<EvolutionaryOperator<List<String>>> operators = new ArrayList<EvolutionaryOperator<List<String>>>(2);
+        if (crossover)
+        {
+            operators.add(new ListOrderCrossover<String>());
+        }
+        if (mutation)
+        {
+            operators.add(new ListOrderMutation<String>(new PoissonGenerator(1.5, rng),
+                                                        new PoissonGenerator(1.5, rng)));
+        }
+
+        EvolutionaryOperator<List<String>> pipeline = new EvolutionPipeline<List<String>>(operators);
+
+        CandidateFactory<List<String>> candidateFactory
+            = new ListPermutationFactory<String>(new LinkedList<String>(cities));
+        EvolutionEngine<List<String>> engine
+            = new GenerationalEvolutionEngine<List<String>>(candidateFactory,
+                                                            pipeline,
+                                                            new RouteEvaluator(distances),
+                                                            selectionStrategy,
+                                                            rng);
+        if (progressListener != null)
+        {
+            engine.addEvolutionObserver(new EvolutionObserver<List<String>>()
+            {
+                public void populationUpdate(PopulationData<? extends List<String>> data)
+                {
+                    progressListener.updateProgress(((double) data.getGenerationNumber() + 1) / generationCount * 100);
+                }
+            });
+        }
+        return engine.evolve(populationSize,
+                             eliteCount,
+                             new GenerationCount(generationCount));
+    }
+}
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/travellingsalesman/ExecutionPanel.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/travellingsalesman/ExecutionPanel.java
new file mode 100644
index 0000000..e4d5be0
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/travellingsalesman/ExecutionPanel.java
@@ -0,0 +1,107 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.travellingsalesman;
+
+import java.awt.BorderLayout;
+import java.awt.Font;
+import java.awt.event.ActionListener;
+import javax.swing.BorderFactory;
+import javax.swing.JButton;
+import javax.swing.JPanel;
+import javax.swing.JProgressBar;
+import javax.swing.JScrollPane;
+import javax.swing.JTextArea;
+import javax.swing.SwingUtilities;
+
+/**
+ * Panel for controlling the execution of the Travelling Salesman applet.
+ * Contains controls for starting and stopping the route-finding algorithms
+ * and for displaying progress and results. 
+ * @author Daniel Dyer
+ */
+final class ExecutionPanel extends JPanel implements ProgressListener
+{
+    private final JButton startButton;
+    private final JTextArea output;
+    private final JScrollPane scroller;
+    private final JProgressBar progressBar;
+
+
+    ExecutionPanel()
+    {
+        super(new BorderLayout());        
+        JPanel controlPanel = new JPanel(new BorderLayout());
+        startButton = new JButton("Start");
+        controlPanel.add(startButton, BorderLayout.WEST);
+        progressBar = new JProgressBar(0, 100);
+        controlPanel.add(progressBar, BorderLayout.CENTER);
+        add(controlPanel, BorderLayout.NORTH);
+        output = new JTextArea();
+        output.setEditable(false);
+        output.setLineWrap(true);
+        output.setWrapStyleWord(true);
+        output.setFont(new Font("Monospaced", Font.PLAIN, 12));
+        scroller = new JScrollPane(output);
+        scroller.setBorder(BorderFactory.createTitledBorder("Results"));
+        add(scroller, BorderLayout.CENTER);
+    }
+
+
+    /**
+     * Adds logic to the start button so that something happens when
+     * it is clicked.
+     * @param actionListener The action to perform when the button is
+     * clicked.
+     */
+    public void addActionListener(ActionListener actionListener)
+    {
+        startButton.addActionListener(actionListener);
+    }
+
+
+    /**
+     * Updates the position of the progress bar.
+     */
+    public void updateProgress(final double percentComplete)
+    {
+        SwingUtilities.invokeLater(new Runnable()
+        {
+            public void run()
+            {
+                progressBar.setValue((int) percentComplete);
+            }
+        });
+    }
+
+
+    /**
+     * Appends the specified text to this panel's text area.
+     * @param text The text to append.
+     */
+    public void appendOutput(String text)
+    {
+        output.append(text);
+    }
+
+    
+    @Override
+    public void setEnabled(boolean b)
+    {
+        startButton.setEnabled(b);
+        scroller.setEnabled(b);
+        super.setEnabled(b);
+    }
+}
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/travellingsalesman/ItineraryPanel.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/travellingsalesman/ItineraryPanel.java
new file mode 100644
index 0000000..0e5c154
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/travellingsalesman/ItineraryPanel.java
@@ -0,0 +1,114 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.travellingsalesman;
+
+import java.awt.BorderLayout;
+import java.awt.GridLayout;
+import java.awt.event.ActionEvent;
+import java.awt.event.ActionListener;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.List;
+import java.util.Set;
+import java.util.TreeSet;
+import javax.swing.BorderFactory;
+import javax.swing.JButton;
+import javax.swing.JCheckBox;
+import javax.swing.JPanel;
+
+/**
+ * Component for selecting which cities are to be visited by the
+ * travelling salesman.
+ * @author Daniel Dyer
+ */
+final class ItineraryPanel extends JPanel
+{
+    private final Collection<JCheckBox> checkBoxes;
+    private final JButton selectAllButton;
+    private final JButton clearButton;
+
+    ItineraryPanel(List<String> cities)
+    {
+        super(new BorderLayout());
+
+        JPanel checkBoxPanel = new JPanel(new GridLayout(0, 1));
+        checkBoxes = new ArrayList<JCheckBox>(cities.size());
+        for (String city : cities)
+        {
+            JCheckBox checkBox = new JCheckBox(city, false);
+            checkBox.setName(city); // Helps to find the checkbox from a unit test.
+            checkBoxes.add(checkBox);
+            checkBoxPanel.add(checkBox);
+        }
+        add(checkBoxPanel, BorderLayout.CENTER);
+
+        JPanel buttonPanel = new JPanel(new GridLayout(2, 1));
+        selectAllButton = new JButton("Select All");
+        selectAllButton.setName("All");
+        buttonPanel.add(selectAllButton);
+        clearButton = new JButton("Clear Selection");
+        clearButton.setName("None");
+        buttonPanel.add(clearButton);
+        ActionListener buttonListener = new ActionListener()
+        {
+
+            public void actionPerformed(ActionEvent actionEvent)
+            {
+                boolean select = actionEvent.getSource() == selectAllButton;
+                for (JCheckBox checkBox : checkBoxes)
+                {
+                    checkBox.setSelected(select);
+                }
+            }
+        };
+        selectAllButton.addActionListener(buttonListener);
+        clearButton.addActionListener(buttonListener);
+        add(buttonPanel, BorderLayout.SOUTH);
+
+        setBorder(BorderFactory.createTitledBorder("Itinerary"));
+    }
+
+
+    /**
+     * Returns the cities that have been selected as part of the itinerary.
+     * @return A list of cities.
+     */
+    public Collection<String> getSelectedCities()
+    {
+        Set<String> cities = new TreeSet<String>();
+        for (JCheckBox checkBox : checkBoxes)
+        {
+            if (checkBox.isSelected())
+            {
+                cities.add(checkBox.getText());
+            }
+        }
+        return cities;
+    }
+
+
+    @Override
+    public void setEnabled(boolean b)
+    {
+        for (JCheckBox checkBox : checkBoxes)
+        {
+            checkBox.setEnabled(b);
+        }
+        selectAllButton.setEnabled(b);
+        clearButton.setEnabled(b);
+        super.setEnabled(b);
+    }
+}
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/travellingsalesman/ProgressListener.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/travellingsalesman/ProgressListener.java
new file mode 100644
index 0000000..661a5e5
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/travellingsalesman/ProgressListener.java
@@ -0,0 +1,31 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.travellingsalesman;
+
+/**
+ * Call-back interface for keeping track of the progress of a
+ * {@link TravellingSalesmanStrategy} implementation.
+ * @author Daniel Dyer
+ */
+public interface ProgressListener
+{
+    /**
+     * Call-back method that informs the implementing object
+     * of the current completion percentage.
+     * @param percentComplete A percentage between 0 and 100.
+     */
+    void updateProgress(double percentComplete);
+}
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/travellingsalesman/RouteEvaluator.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/travellingsalesman/RouteEvaluator.java
new file mode 100644
index 0000000..144d593
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/travellingsalesman/RouteEvaluator.java
@@ -0,0 +1,74 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.travellingsalesman;
+
+import java.util.List;
+import org.uncommons.watchmaker.framework.FitnessEvaluator;
+
+/**
+ * Fitness evalator that measures the total distance of a route in the travelling salesman
+ * problem.  The fitness score of a route is the total distance (in km).  A route
+ * is represented as a list of cities in the order that they will be visited.
+ * The last leg of the journey is from the last city in the list back to the
+ * first.
+ * @author Daniel Dyer
+ */
+public class RouteEvaluator implements FitnessEvaluator<List<String>>
+{
+    private final DistanceLookup distances;
+
+
+    /**
+     * @param distances Provides distances between a set of cities.
+     */
+    public RouteEvaluator(DistanceLookup distances)
+    {
+        this.distances = distances;
+    }
+
+
+    /**
+     * Calculates the length of an evolved route. 
+     * @param candidate The route to evaluate.
+     * @param population {@inheritDoc}
+     * @return The total distance (in kilometres) of a journey that visits
+     * each city in order and returns to the starting point.
+     */
+    public double getFitness(List<String> candidate,
+                             List<? extends List<String>> population)
+    {
+        int totalDistance = 0;
+        int cityCount = candidate.size();
+        for (int i = 0; i < cityCount; i++)
+        {
+            int nextIndex = i < cityCount - 1 ? i + 1 : 0;
+            totalDistance += distances.getDistance(candidate.get(i),
+                                                   candidate.get(nextIndex));
+        }
+        return totalDistance;
+    }
+
+
+    /**
+     * {@inheritDoc}
+     * Returns false since shorter distances represent fitter candidates.
+     * @return false
+     */
+    public boolean isNatural()
+    {
+        return false;
+    }
+}
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/travellingsalesman/StrategyPanel.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/travellingsalesman/StrategyPanel.java
new file mode 100644
index 0000000..99f727d
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/travellingsalesman/StrategyPanel.java
@@ -0,0 +1,92 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.travellingsalesman;
+
+import java.awt.BorderLayout;
+import java.awt.event.ItemEvent;
+import java.awt.event.ItemListener;
+import javax.swing.BorderFactory;
+import javax.swing.ButtonGroup;
+import javax.swing.JPanel;
+import javax.swing.JRadioButton;
+
+/**
+ * Panel for configuring a route-finding strategy for the travelling
+ * salesman problem.
+ * @author Daniel Dyer
+ */
+final class StrategyPanel extends JPanel
+{
+    private final DistanceLookup distances;
+    private final JRadioButton evolutionOption;
+    private final JRadioButton bruteForceOption;
+    private final EvolutionPanel evolutionPanel;
+
+    /**
+     * Creates a panel with components for controlling the route-finding
+     * strategy.
+     * @param distances Data used by the strategy in order to calculate
+     * shortest routes.
+     */
+    StrategyPanel(DistanceLookup distances)
+    {
+        super(new BorderLayout());
+        this.distances = distances;
+        evolutionOption = new JRadioButton("Evolution", true);
+        evolutionOption.setName("EvolutionOption"); // Helps to find the radio button from a unit test.
+        bruteForceOption = new JRadioButton("Brute Force", false);
+        bruteForceOption.setName("BruteForceOption"); // Helps to find the radio button from a unit test.
+        evolutionOption.addItemListener(new ItemListener()
+        {
+            public void itemStateChanged(ItemEvent itemEvent)
+            {
+                evolutionPanel.setEnabled(evolutionOption.isSelected());
+            }
+        });
+        ButtonGroup strategyGroup = new ButtonGroup();
+        strategyGroup.add(evolutionOption);
+        strategyGroup.add(bruteForceOption);
+        evolutionPanel = new EvolutionPanel(distances);
+        evolutionPanel.setName("EvolutionPanel"); // Helps to find the panel from a unit test.
+        add(evolutionOption, BorderLayout.NORTH);
+        add(evolutionPanel, BorderLayout.CENTER);
+        add(bruteForceOption, BorderLayout.SOUTH);
+        setBorder(BorderFactory.createTitledBorder("Route-Finding Strategy"));
+    }
+
+
+    public TravellingSalesmanStrategy getStrategy()
+    {
+        if (bruteForceOption.isSelected())
+        {
+            return new BruteForceTravellingSalesman(distances);
+        }
+        else
+        {
+            return evolutionPanel.getStrategy();
+        }
+    }
+
+
+    @Override
+    public void setEnabled(boolean b)
+    {
+        evolutionOption.setEnabled(b);
+        bruteForceOption.setEnabled(b);
+        evolutionPanel.setEnabled(b && evolutionOption.isSelected());
+        super.setEnabled(b);
+    }
+}
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/travellingsalesman/TravellingSalesmanApplet.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/travellingsalesman/TravellingSalesmanApplet.java
new file mode 100644
index 0000000..96490b2
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/travellingsalesman/TravellingSalesmanApplet.java
@@ -0,0 +1,185 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.travellingsalesman;
+
+import java.awt.BorderLayout;
+import java.awt.Container;
+import java.awt.event.ActionEvent;
+import java.awt.event.ActionListener;
+import java.util.Collection;
+import java.util.List;
+import javax.swing.JOptionPane;
+import javax.swing.JPanel;
+import org.uncommons.swing.SwingBackgroundTask;
+import org.uncommons.watchmaker.examples.AbstractExampleApplet;
+import org.uncommons.watchmaker.framework.FitnessEvaluator;
+
+/**
+ * Applet for comparing evolutionary and brute force approaches to the
+ * Travelling Salesman problem.
+ * @author Daniel Dyer
+ */
+public final class TravellingSalesmanApplet extends AbstractExampleApplet
+{
+    private final DistanceLookup distances = new EuropeanDistanceLookup();
+    private final FitnessEvaluator<List<String>> evaluator = new RouteEvaluator(distances);
+
+    private ItineraryPanel itineraryPanel;
+    private StrategyPanel strategyPanel;
+    private ExecutionPanel executionPanel;
+
+
+    /**
+     * Initialise and layout the GUI.
+     * @param container The Swing component that will contain the GUI controls.
+     */
+    @Override
+    protected void prepareGUI(Container container)
+    {
+        itineraryPanel = new ItineraryPanel(distances.getKnownCities());
+        strategyPanel = new StrategyPanel(distances);
+        executionPanel = new ExecutionPanel();
+
+        container.add(itineraryPanel, BorderLayout.WEST);
+        JPanel innerPanel = new JPanel(new BorderLayout());
+        innerPanel.add(strategyPanel, BorderLayout.NORTH);
+        innerPanel.add(executionPanel, BorderLayout.CENTER);
+        container.add(innerPanel, BorderLayout.CENTER);
+
+        executionPanel.addActionListener(new ActionListener()
+        {
+            public void actionPerformed(ActionEvent actionEvent)
+            {
+                Collection<String> cities = itineraryPanel.getSelectedCities();
+                if (cities.size() < 4)
+                {
+                    JOptionPane.showMessageDialog(TravellingSalesmanApplet.this,
+                                                  "Itinerary must include at least 4 cities.",
+                                                  "Error",
+                                                  JOptionPane.ERROR_MESSAGE);
+                }
+                else
+                {
+                    try
+                    {
+                        setEnabled(false);
+                        createTask(cities).execute();
+                    }
+                    catch (IllegalArgumentException ex)
+                    {
+                        JOptionPane.showMessageDialog(TravellingSalesmanApplet.this,
+                                                      ex.getMessage(),
+                                                      "Error",
+                                                      JOptionPane.ERROR_MESSAGE);
+                        setEnabled(true);
+                    }
+                }
+            }
+        });
+        container.validate();
+    }
+
+
+    /**
+     * Helper method to create a background task for running the travelling
+     * salesman algorithm.
+     * @param cities The set of cities to generate a route for.
+     * @return A Swing task that will execute on a background thread and update
+     * the GUI when it is done.
+     */
+    private SwingBackgroundTask<List<String>> createTask(final Collection<String> cities)
+    {
+        final TravellingSalesmanStrategy strategy = strategyPanel.getStrategy();
+        return new SwingBackgroundTask<List<String>>()
+        {
+            private long elapsedTime = 0;
+
+            @Override
+            protected List<String> performTask()
+            {
+                long startTime = System.currentTimeMillis();
+                List<String> result = strategy.calculateShortestRoute(cities, executionPanel);
+                elapsedTime = System.currentTimeMillis() - startTime;
+                return result;
+            }
+
+            @Override
+            protected void postProcessing(List<String> result)
+            {
+                executionPanel.appendOutput(createResultString(strategy.getDescription(),
+                                                               result,
+                                                               evaluator.getFitness(result, null),
+                                                               elapsedTime));
+                setEnabled(true);
+            }
+        };
+    }
+
+
+    /**
+     * Helper method for formatting a result as a string for display.
+     */
+    private String createResultString(String strategyDescription,
+                                      List<String> shortestRoute,
+                                      double distance,
+                                      long elapsedTime)
+    {
+        StringBuilder buffer = new StringBuilder();
+        buffer.append('[');
+        buffer.append(strategyDescription);
+        buffer.append("]\n");
+        buffer.append("ROUTE: ");
+        for (String s : shortestRoute)
+        {
+            buffer.append(s);
+            buffer.append(" -> ");
+        }
+        buffer.append(shortestRoute.get(0));
+        buffer.append('\n');
+        buffer.append("TOTAL DISTANCE: ");
+        buffer.append(String.valueOf(distance));
+        buffer.append("km\n");
+        buffer.append("(Search Time: ");
+        double seconds = (double) elapsedTime / 1000;
+        buffer.append(String.valueOf(seconds));
+        buffer.append(" seconds)\n\n");
+        return buffer.toString();
+    }
+
+
+    /**
+     * Toggles whether the controls are enabled for input or not.
+     * @param b Enables the controls if this flag is true, disables them otherwise.
+     */
+    @Override
+    public void setEnabled(boolean b)
+    {
+        itineraryPanel.setEnabled(b);
+        strategyPanel.setEnabled(b);
+        executionPanel.setEnabled(b);
+        super.setEnabled(b);
+    }
+
+
+    /**
+     * Entry point for running this example as an application rather than an applet.
+     * @param args Program arguments (ignored).
+     */
+    public static void main(String[] args)
+    {
+        new TravellingSalesmanApplet().displayInFrame("Watchmaker Framework - Travelling Salesman Example");
+    }
+}
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/travellingsalesman/TravellingSalesmanStrategy.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/travellingsalesman/TravellingSalesmanStrategy.java
new file mode 100644
index 0000000..82f75c8
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/travellingsalesman/TravellingSalesmanStrategy.java
@@ -0,0 +1,44 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.travellingsalesman;
+
+import java.util.Collection;
+import java.util.List;
+
+/**
+ * Defines methods that must be implemented by classes that provide
+ * solutions to the Travelling Salesman problem.
+ * @author Daniel Dyer
+ */
+public interface TravellingSalesmanStrategy
+{
+    /**
+     * @return A description of the strategy.
+     */
+    String getDescription();
+
+    /**
+     * Calculates the shortest round trip distance that visits each
+     * of the specified cities once and returns to the starting point.
+     * @param cities The destination that must each be visited for the route
+     * to be valid.
+     * @param progressListener A call-back for keeping track of the route-finding
+     * algorithm's progress.
+     * @return The shortest route found for the given list of destinations.
+     */
+    List<String> calculateShortestRoute(Collection<String> cities,
+                                        ProgressListener progressListener);
+}
diff --git a/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/travellingsalesman/package-info.java b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/travellingsalesman/package-info.java
new file mode 100644
index 0000000..59f25f5
--- /dev/null
+++ b/watchmaker/examples/src/java/main/org/uncommons/watchmaker/examples/travellingsalesman/package-info.java
@@ -0,0 +1,21 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+/**
+ * An evolutionary approach to tackling the well-known Travelling Salesman
+ * problem.
+ * @author Daniel Dyer
+ */
+package org.uncommons.watchmaker.examples.travellingsalesman;
diff --git a/watchmaker/examples/src/java/resources/org/uncommons/watchmaker/examples/monalisa/lighthouse.jpg b/watchmaker/examples/src/java/resources/org/uncommons/watchmaker/examples/monalisa/lighthouse.jpg
new file mode 100644
index 0000000..fcd57f6
--- /dev/null
+++ b/watchmaker/examples/src/java/resources/org/uncommons/watchmaker/examples/monalisa/lighthouse.jpg
diff --git a/watchmaker/examples/src/java/resources/org/uncommons/watchmaker/examples/monalisa/monalisa.jpg b/watchmaker/examples/src/java/resources/org/uncommons/watchmaker/examples/monalisa/monalisa.jpg
new file mode 100644
index 0000000..61ae626
--- /dev/null
+++ b/watchmaker/examples/src/java/resources/org/uncommons/watchmaker/examples/monalisa/monalisa.jpg
diff --git a/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/AbstractExampleAppletTest.java b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/AbstractExampleAppletTest.java
new file mode 100644
index 0000000..f762147
--- /dev/null
+++ b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/AbstractExampleAppletTest.java
@@ -0,0 +1,94 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples;
+
+import java.awt.BorderLayout;
+import java.awt.Container;
+import javax.swing.JFrame;
+import javax.swing.JLabel;
+import javax.swing.SwingUtilities;
+import org.fest.swing.core.BasicRobot;
+import org.fest.swing.core.Robot;
+import org.fest.swing.core.matcher.FrameMatcher;
+import org.fest.swing.fixture.FrameFixture;
+import org.testng.annotations.AfterMethod;
+import org.testng.annotations.BeforeMethod;
+import org.testng.annotations.Test;
+
+/**
+ * Unit test for the {@link AbstractExampleAppletTest} class.
+ * @author Daniel Dyer
+ */
+public class AbstractExampleAppletTest
+{
+    private Robot robot;
+
+    @BeforeMethod
+    public void prepare()
+    {
+        robot = BasicRobot.robotWithNewAwtHierarchy();
+    }
+
+
+    @AfterMethod
+    public void cleanUp()
+    {
+        robot.cleanUp();
+        robot = null;
+    }
+
+    
+    @Test(groups = "display-required") // Will fail if run in a headless environment.
+    public void testPreparationOnEDT()
+    {
+        final boolean[] onEDT = new boolean[1];
+        AbstractExampleApplet applet = new AbstractExampleApplet()
+        {
+            @Override
+            protected void prepareGUI(Container container)
+            {
+                onEDT[0] = SwingUtilities.isEventDispatchThread();
+            }
+        };
+        applet.init();
+        assert onEDT[0] : "Prepare method was not called on Event Dispatch Thread.";
+    }
+
+
+    @Test(groups = "display-required") // Will fail if run in a headless environment.
+    public void testDisplayInFrame()
+    {
+        AbstractExampleApplet applet = new AbstractExampleApplet()
+        {
+            @Override
+            protected void prepareGUI(Container container)
+            {
+                JLabel label = new JLabel("Test");
+                label.setName("Test");
+                container.add(label, BorderLayout.CENTER);
+            }
+        };
+        applet.displayInFrame("ExampleFrame");
+        robot.waitForIdle();
+        // There ought to be a visible frame containing the example GUI.
+        JFrame frame = (JFrame) robot.finder().find(FrameMatcher.withTitle("ExampleFrame").andShowing());
+        frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
+
+        FrameFixture frameFixture = new FrameFixture(robot, frame);
+        assert frameFixture.label("Test").component().isShowing() : "GUI not displayed correctly.";        
+        frameFixture.close();
+    }
+}
diff --git a/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/ExamplesTestUtils.java b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/ExamplesTestUtils.java
new file mode 100644
index 0000000..5affc17
--- /dev/null
+++ b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/ExamplesTestUtils.java
@@ -0,0 +1,48 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples;
+
+import java.util.Random;
+import org.uncommons.maths.random.XORShiftRNG;
+
+/**
+ * Utility methods for Watchmaker examples unit tests.  Provides
+ * access to shared resources used by tests.
+ * @author Daniel Dyer
+ */
+public final class ExamplesTestUtils
+{
+    private static final Random RNG = new XORShiftRNG();
+
+    private ExamplesTestUtils()
+    {
+        // Prevent instantiation.
+    }
+
+
+    /**
+     * Returns the singleton RNG shared by all tests.  It might be preferable
+     * to have a separate RNG for each test (for true separation) but this
+     * causes problems.  Seeding dozens of RNGs can exhaust the system's
+     * available entropy (the Uncommons Maths RNGs seed themselves from
+     * /dev/random by default).
+     * @return A random number generator.
+     */
+    public static Random getRNG()
+    {
+        return RNG;
+    }
+}
diff --git a/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/biomorphs/BiomorphFactoryTest.java b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/biomorphs/BiomorphFactoryTest.java
new file mode 100644
index 0000000..c1d1cce
--- /dev/null
+++ b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/biomorphs/BiomorphFactoryTest.java
@@ -0,0 +1,51 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.biomorphs;
+
+import java.util.List;
+import org.testng.annotations.Test;
+import org.uncommons.watchmaker.examples.ExamplesTestUtils;
+import org.uncommons.watchmaker.framework.CandidateFactory;
+
+/**
+ * Unit test for the biomorph candidate factory.
+ * @author Daniel Dyer
+ */
+public class BiomorphFactoryTest
+{
+    /**
+     * Ensures that biomorphs created by the factory are valid.
+     */
+    @Test
+    public void testValidity()
+    {
+        CandidateFactory<Biomorph> factory = new BiomorphFactory();
+        List<Biomorph> biomorphs = factory.generateInitialPopulation(20, ExamplesTestUtils.getRNG());
+        for (Biomorph biomorph : biomorphs)
+        {
+            // Returns 9 genes, last one is the length gene.
+            int[] genes = biomorph.getGenotype();
+            for (int i = 0; i < Biomorph.GENE_COUNT - 1; i++)
+            {
+                assert genes[i] >= Biomorph.GENE_MIN && genes[i] <= Biomorph.GENE_MAX
+                    : "Gene " + i + " is out of range: " + genes[i];
+            }
+            int length = biomorph.getLengthPhenotype();
+            assert length >= Biomorph.LENGTH_GENE_MIN && length <= Biomorph.LENGTH_GENE_MAX
+                : "Length gene is out of range: " + length;
+        }
+    }
+}
diff --git a/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/biomorphs/BiomorphTest.java b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/biomorphs/BiomorphTest.java
new file mode 100644
index 0000000..b62c8a2
--- /dev/null
+++ b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/biomorphs/BiomorphTest.java
@@ -0,0 +1,59 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.biomorphs;
+
+import java.util.Arrays;
+import org.testng.annotations.Test;
+
+/**
+ * Some basic sanity checks for the {@link Biomorph} type used in the
+ * interactive evolution example program.
+ * @author Daniel Dyer
+ */
+public class BiomorphTest
+{
+    @Test(expectedExceptions = IllegalArgumentException.class)
+    public void testInsufficientGenes()
+    {
+        new Biomorph(new int[Biomorph.GENE_COUNT - 1]);
+    }
+
+    @Test(expectedExceptions = IllegalArgumentException.class)
+    public void testTooManyGenes()
+    {
+        new Biomorph(new int[Biomorph.GENE_COUNT + 1]);
+    }
+
+
+    @Test
+    public void testEquality()
+    {
+        Biomorph biomorph1 = new Biomorph(new int[Biomorph.GENE_COUNT]);
+        Biomorph biomorph2 = new Biomorph(new int[Biomorph.GENE_COUNT]);
+        int[] genes = new int[Biomorph.GENE_COUNT];
+        Arrays.fill(genes, 2);
+        Biomorph biomorph3 = new Biomorph(genes);
+
+        assert biomorph1.equals(biomorph1) : "Equality must be reflexive.";
+        assert biomorph1.equals(biomorph2) : "Biomorphs with identical genes should be considered equal.";
+        assert biomorph2.equals(biomorph1) : "Equality must be reflective.";
+        assert biomorph1.hashCode() == biomorph2.hashCode() : "Equal objects must have identical hash codes.";
+        assert !biomorph1.equals(biomorph3) : "Biomorphs with different genes should not be considered equal.";
+
+        assert !biomorph1.equals(null) : "No object should be considered equal to a null reference.";
+        assert !biomorph3.equals(genes) : "Biomorphs should not be considered equal to objects of different types.";
+    }
+}
diff --git a/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/biomorphs/DawkinsBiomorphMutationTest.java b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/biomorphs/DawkinsBiomorphMutationTest.java
new file mode 100644
index 0000000..09efe3e
--- /dev/null
+++ b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/biomorphs/DawkinsBiomorphMutationTest.java
@@ -0,0 +1,72 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.biomorphs;
+
+import java.util.ArrayList;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+import org.testng.annotations.Test;
+import org.uncommons.watchmaker.examples.ExamplesTestUtils;
+import org.uncommons.watchmaker.framework.EvolutionaryOperator;
+
+/**
+ * Unit test for non-random mutation used by Biomorph example application.
+ * @author Daniel Dyer
+ */
+public class DawkinsBiomorphMutationTest
+{
+    /**
+     * Ensure that each possible mutation occurs exactly once.
+     */
+    @Test
+    public void testMutations()
+    {
+        Biomorph source = new Biomorph(new int[]{-5, -4, -3, -2, -1, 0, 1, 2, 8});
+        List<Biomorph> originalPopulation = new ArrayList<Biomorph>(18);
+        for (int i = 0; i < 18; i++)
+        {
+            originalPopulation.add(source);
+        }
+        EvolutionaryOperator<Biomorph> mutation = new DawkinsBiomorphMutation();
+        List<Biomorph> mutatedPopulation = mutation.apply(originalPopulation,
+                                                          ExamplesTestUtils.getRNG()); // RNG should be ignored.
+        assert mutatedPopulation.size() == originalPopulation.size() : "Mutated population is wrong size.";
+        // Lazy way of checking for duplicates.  Add all mutations to a set.  If there are any
+        // duplicates, the size of the set will be shorter than the list.
+        Set<Biomorph> distinctBiomorphs = new HashSet<Biomorph>(mutatedPopulation);
+        assert distinctBiomorphs.size() == mutatedPopulation.size() : "Mutated population contains duplicates.";
+        // Check for each of the expected mutations (mutations should differ from the original in only one gene).
+        assert distinctBiomorphs.contains(new Biomorph(new int[]{5, -4, -3, -2, -1, 0, 1, 2, 8})) : "Missing mutation.";
+        assert distinctBiomorphs.contains(new Biomorph(new int[]{-4, -4, -3, -2, -1, 0, 1, 2, 8})) : "Missing mutation.";
+        assert distinctBiomorphs.contains(new Biomorph(new int[]{-5, -5, -3, -2, -1, 0, 1, 2, 8})) : "Missing mutation.";
+        assert distinctBiomorphs.contains(new Biomorph(new int[]{-5, -3, -3, -2, -1, 0, 1, 2, 8})) : "Missing mutation.";
+        assert distinctBiomorphs.contains(new Biomorph(new int[]{-5, -4, -4, -2, -1, 0, 1, 2, 8})) : "Missing mutation.";
+        assert distinctBiomorphs.contains(new Biomorph(new int[]{-5, -4, -2, -2, -1, 0, 1, 2, 8})) : "Missing mutation.";
+        assert distinctBiomorphs.contains(new Biomorph(new int[]{-5, -4, -3, -3, -1, 0, 1, 2, 8})) : "Missing mutation.";
+        assert distinctBiomorphs.contains(new Biomorph(new int[]{-5, -4, -3, -1, -1, 0, 1, 2, 8})) : "Missing mutation.";
+        assert distinctBiomorphs.contains(new Biomorph(new int[]{-5, -4, -3, -2, -2, 0, 1, 2, 8})) : "Missing mutation.";
+        assert distinctBiomorphs.contains(new Biomorph(new int[]{-5, -4, -3, -2, 0, 0, 1, 2, 8})) : "Missing mutation.";
+        assert distinctBiomorphs.contains(new Biomorph(new int[]{-5, -4, -3, -2, -1, -1, 1, 2, 8})) : "Missing mutation.";
+        assert distinctBiomorphs.contains(new Biomorph(new int[]{-5, -4, -3, -2, -1, 1, 1, 2, 8})) : "Missing mutation.";
+        assert distinctBiomorphs.contains(new Biomorph(new int[]{-5, -4, -3, -2, -1, 0, 0, 2, 8})) : "Missing mutation.";
+        assert distinctBiomorphs.contains(new Biomorph(new int[]{-5, -4, -3, -2, -1, 0, 2, 2, 8})) : "Missing mutation.";
+        assert distinctBiomorphs.contains(new Biomorph(new int[]{-5, -4, -3, -2, -1, 0, 1, 1, 8})) : "Missing mutation.";
+        assert distinctBiomorphs.contains(new Biomorph(new int[]{-5, -4, -3, -2, -1, 0, 1, 3, 8})) : "Missing mutation.";
+        assert distinctBiomorphs.contains(new Biomorph(new int[]{-5, -4, -3, -2, -1, 0, 1, 2, 7})) : "Missing mutation.";
+        assert distinctBiomorphs.contains(new Biomorph(new int[]{-5, -4, -3, -2, -1, 0, 1, 2, 1})) : "Missing mutation.";
+    }
+}
diff --git a/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/biomorphs/RandomBiomorphMutationTest.java b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/biomorphs/RandomBiomorphMutationTest.java
new file mode 100644
index 0000000..5c0890d
--- /dev/null
+++ b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/biomorphs/RandomBiomorphMutationTest.java
@@ -0,0 +1,59 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.biomorphs;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Random;
+import org.testng.annotations.Test;
+import org.uncommons.maths.random.Probability;
+import org.uncommons.watchmaker.examples.ExamplesTestUtils;
+import org.uncommons.watchmaker.framework.EvolutionaryOperator;
+
+/**
+ * Unit test for random mutation operator for biomorphs.
+ * @author Daniel Dyer
+ */
+public class RandomBiomorphMutationTest
+{
+    @Test
+    public void testValidity()
+    {
+        EvolutionaryOperator<Biomorph> mutation = new RandomBiomorphMutation(Probability.ONE); // Mutate every gene.
+        List<Biomorph> population = new ArrayList<Biomorph>(3);
+        population.add(new Biomorph(new int[]{5, -4, -3, -2, -1, 0, 1, 2, 8}));
+        population.add(new Biomorph(new int[]{-5, 4, 4, -5, 5, 3, 0, 2, 2}));
+        population.add(new Biomorph(new int[]{-4, -1, 0, 0, 3, 0, 4, 5, 4}));
+        Random rng = ExamplesTestUtils.getRNG();
+        for (int i = 0; i < 20; i++) // Perform several mutations to cover more possibilties.
+        {
+            population = mutation.apply(population, rng);
+            for (Biomorph biomorph : population)
+            {
+                // Returns 9 genes, last one is the length gene.
+                int[] genes = biomorph.getGenotype();
+                for (int j = 0; j < Biomorph.GENE_COUNT - 1; j++)
+                {
+                    assert genes[j] >= Biomorph.GENE_MIN && genes[j] <= Biomorph.GENE_MAX
+                        : "Gene " + j + " is out of range: " + genes[j];
+                }
+                int length = biomorph.getLengthPhenotype();
+                assert length >= Biomorph.LENGTH_GENE_MIN && length <= Biomorph.LENGTH_GENE_MAX
+                    : "Length gene is out of range: " + length;
+            }
+        }
+    }
+}
diff --git a/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/bits/BitsExampleTest.java b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/bits/BitsExampleTest.java
new file mode 100644
index 0000000..737ed55
--- /dev/null
+++ b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/bits/BitsExampleTest.java
@@ -0,0 +1,34 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.bits;
+
+import org.testng.annotations.Test;
+import org.uncommons.maths.binary.BitString;
+
+/**
+ * Simple unit test for the bits example.  Makes sure that the evolution engine
+ * eventually returns the expected result.
+ * @author Daniel Dyer
+ */
+public class BitsExampleTest
+{
+    @Test
+    public void testEvolution()
+    {
+        BitString result = BitsExample.evolveBits(8);
+        assert result.toString().equals("11111111") : "Wrong result returned: " + result.toString();
+    }
+}
diff --git a/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/geneticprogramming/AdditionTest.java b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/geneticprogramming/AdditionTest.java
new file mode 100644
index 0000000..1ad9a46
--- /dev/null
+++ b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/geneticprogramming/AdditionTest.java
@@ -0,0 +1,112 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.geneticprogramming;
+
+import org.testng.annotations.Test;
+
+/**
+ * Simple unit test for the {@link Addition} node type.
+ * @author Daniel Dyer
+ */
+public class AdditionTest
+{
+    @Test
+    public void testEvaluation()
+    {
+        Node node = new Addition(new Constant(1), new Parameter(0));
+        double value = node.evaluate(new double[]{3}); // 1 + 3
+        assert value == 4 : "Wrong result: " + value;
+    }
+
+    @Test
+    public void testStringRepresentation()
+    {
+        Node node = new Addition(new Constant(1), new Constant(3));
+        assert node.print().equals("(1.0 + 3.0)") : "Wrong string representation: " + node.print();
+    }
+
+
+    /**
+     * If the arguments to the add function are both constants then the addition node
+     * should be replaced by a constant node containing the evaluation of this sum.
+     */
+    @Test
+    public void testSimplifyConstants()
+    {
+        Node node = new Addition(new Constant(7), new Constant(5));
+        Node simplified = node.simplify();
+        assert simplified instanceof Constant
+            : "Simplified node should be Constant, is " + simplified.getClass().getSimpleName();
+        assert simplified.evaluate(BinaryNode.NO_ARGS) == node.evaluate(BinaryNode.NO_ARGS) : "Simplified answer differs.";
+        assert simplified.evaluate(BinaryNode.NO_ARGS) == 12;
+
+    }
+
+
+
+    /**
+     * Test that simplification doesn't cause any problems when the expression is already as simple
+     * as possible.
+     */
+    @Test
+    public void testSimplifySimplest()
+    {
+        Node node = new Addition(new Parameter(0), new Constant(1));
+        Node simplified = node.simplify();
+        assert simplified == node : "Expression should not have been changed.";
+    }
+
+
+    /**
+     * Make sure that sub-nodes are simplified.
+     */
+    @Test
+    public void testSimplifySubNode()
+    {
+        Node node = new Addition(new Parameter(0),
+                                 new Addition(new Constant(3), new Constant(2)));
+        Node simplified = node.simplify();
+        assert simplified instanceof Addition
+            : "Simplified node should be Addition, is " + simplified.getClass().getSimpleName();
+        double[] args = new double[]{5}; // Provides a value for the parameter nodes.
+        assert simplified.evaluate(args) == node.evaluate(args) : "Simplified answer differs.";
+        assert simplified.countNodes() < node.countNodes() : "Should be fewer nodes after simplification.";
+    }
+
+
+    @Test
+    public void testSimplifyAddZero()
+    {
+        Node node = new Addition(new Parameter(0), new Constant(0));
+        Node simplified = node.simplify();
+        assert simplified instanceof Parameter
+            : "Simplified node should be Parameter, is " + simplified.getClass().getSimpleName();
+        double[] args = new double[]{5}; // Provides a value for the parameter nodes.
+        assert simplified.evaluate(args) == node.evaluate(args) : "Simplified answer differs.";
+    }
+
+
+    @Test
+    public void testSimplifyAddToZero()
+    {
+        Node node = new Addition(new Constant(0), new Parameter(0));
+        Node simplified = node.simplify();
+        assert simplified instanceof Parameter
+            : "Simplified node should be Parameter, is " + simplified.getClass().getSimpleName();
+        double[] args = new double[]{5}; // Provides a value for the parameter nodes.
+        assert simplified.evaluate(args) == node.evaluate(args) : "Simplified answer differs.";
+    }
+}
diff --git a/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/geneticprogramming/ConstantTest.java b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/geneticprogramming/ConstantTest.java
new file mode 100644
index 0000000..1a5eb36
--- /dev/null
+++ b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/geneticprogramming/ConstantTest.java
@@ -0,0 +1,55 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.geneticprogramming;
+
+import org.testng.annotations.Test;
+
+/**
+ * Unit test for the {@link Constant} node type.
+ * @author Daniel Dyer
+ */
+public class ConstantTest
+{
+    @Test
+    public void testEquality()
+    {
+        Constant zero = new Constant(0);
+        Constant one = new Constant(1);
+        Constant anotherOne = new Constant(1);
+
+        assert zero.equals(zero) : "Equality must be reflexive.";
+        assert one.equals(anotherOne) : "Same-valued constants must be equal.";
+        assert anotherOne.equals(one) : "Equality must be symmetric.";
+        assert one.hashCode() == anotherOne.hashCode() : "Equal objects must have equal hash codes.";
+        assert !zero.equals(one) : "Different valued constants must be non-equal.";
+        assert !zero.equals(null) : "No non-null object should not be considered equal to null.";
+        assert !zero.equals(Double.valueOf(0)) : "Objects of different types should not be equal.";
+    }
+
+
+    @Test(expectedExceptions = IndexOutOfBoundsException.class)
+    public void testGetInvalidNodeIndex()
+    {
+        new Constant(1).getNode(1); // Should throw an exception.
+    }
+
+
+    @Test(expectedExceptions = IndexOutOfBoundsException.class)
+    public void testReplaceInvalidNodeIndex()
+    {
+        new Constant(1).replaceNode(1, new Constant(2)); // Should throw an exception.
+    }
+}
diff --git a/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/geneticprogramming/GeneticProgrammingExampleTest.java b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/geneticprogramming/GeneticProgrammingExampleTest.java
new file mode 100644
index 0000000..3d254fd
--- /dev/null
+++ b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/geneticprogramming/GeneticProgrammingExampleTest.java
@@ -0,0 +1,50 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.geneticprogramming;
+
+import java.util.HashMap;
+import java.util.Map;
+import org.testng.annotations.Test;
+
+/**
+ * Test for the {@link GeneticProgrammingExample} example application.
+ * @author Daniel Dyer
+ */
+public class GeneticProgrammingExampleTest
+{
+    @Test
+    public void testApplication()
+    {
+        Map<double[], Double> testData = new HashMap<double[], Double>();
+        testData.put(new double[]{26, 35}, 165.0d);
+        testData.put(new double[]{8, 24}, 64.0d);
+        testData.put(new double[]{20, 1}, 101.0d);
+        testData.put(new double[]{33, 11}, 176.0d);
+        testData.put(new double[]{37, 16}, 201.0d);
+
+        Node evolvedProgram = GeneticProgrammingExample.evolveProgram(testData);
+
+        // Check that evolved program works for test data.
+        double result1 = evolvedProgram.evaluate(new double[]{8, 24});
+        assert result1 == 64.0d : "Incorrect result: " + result1;        
+
+        // Check that the evolved program generalises.
+        double result2 = evolvedProgram.evaluate(new double[]{10, 7});
+        assert result2 == 57.0d : "Incorrect result: " + result2;
+        double result3 = evolvedProgram.evaluate(new double[]{13, 22});
+        assert result3 == 87.0d : "Incorrect result: " + result3;
+    }
+}
diff --git a/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/geneticprogramming/IfThenElseTest.java b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/geneticprogramming/IfThenElseTest.java
new file mode 100644
index 0000000..13ab813
--- /dev/null
+++ b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/geneticprogramming/IfThenElseTest.java
@@ -0,0 +1,248 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.geneticprogramming;
+
+import org.testng.annotations.Test;
+import org.uncommons.maths.random.Probability;
+import org.uncommons.watchmaker.examples.ExamplesTestUtils;
+
+/**
+ * Unit test for the {@link IfThenElse} node type.
+ * @author Daniel Dyer
+ */
+public class IfThenElseTest
+{
+    @Test
+    public void testIfBranch()
+    {
+        Node node = new IfThenElse(new Constant(1),
+                                   new Constant(5),
+                                   new Constant(10));
+        // Condition (1) is true, so result should be 5.
+        double value = node.evaluate(new double[0]);
+        assert value == 5 : "Wrong answer: " + value; 
+    }
+
+
+    @Test
+    public void testElseBranch()
+    {
+        Node node = new IfThenElse(new Constant(0),
+                                   new Constant(5),
+                                   new Constant(10));
+        // Condition (0) is true, so result should be 10.
+        double value = node.evaluate(new double[0]);
+        assert value == 10 : "Wrong answer: " + value; 
+    }
+
+
+    /**
+     * Count nodes when the sub-trees each consist of only a single leaf node.
+     */
+    @Test
+    public void testCountNodesSimple()
+    {
+        Node node = new IfThenElse(new Constant(1), new Constant(2), new Constant(3));
+        int nodeCount = node.countNodes();
+        assert nodeCount == 4 : "Tree has 4 nodes (root + 3 children), not " + nodeCount;
+    }
+
+
+    /**
+     * Count nodes when the sub-trees consist of non-leaf nodes.
+     */
+    @Test
+    public void testCountNodesComplex()
+    {
+        Node node = new IfThenElse(new Addition(new Constant(1), new Constant(2)),
+                                   new Subtraction(new Constant(3), new Constant(4)),
+                                   new Multiplication(new Constant(5), new Constant(6)));
+        int nodeCount = node.countNodes();
+        assert nodeCount == 10 : "Tree has 10 nodes (root + 3 children and 6 grand-children), not " + nodeCount;
+    }
+
+
+    @Test
+    public void testGetNode()
+    {
+        Node condition = new Constant(1);
+        Node then = new Constant(2);
+        Constant sub1 = new Constant(3);
+        Constant sub2 = new Constant(4);
+        Node otherwise = new Addition(sub1, sub2);
+        Node node = new IfThenElse(condition, then, otherwise);
+
+        assert node.getNode(0) == node : "Node zero should be root node.";
+        assert node.getNode(1) == condition : "Node one should be condition node.";
+        assert node.getNode(2) == then : "Node one should be then node.";
+        assert node.getNode(3) == otherwise : "Node one should be else node.";
+        assert node.getNode(4) == sub1 : "Node 4 should be first sub-node of else node.";
+        assert node.getNode(5) == sub2 : "Node 5 should be second sub-node of else node.";
+    }
+
+
+    @Test
+    public void testReplaceRootNode()
+    {
+        Node node = new IfThenElse(new Constant(1), new Constant(2), new Constant(3));
+        Constant constant = new Constant(0);
+        Node newNode = node.replaceNode(0, constant);
+        assert newNode == constant : "Root node should be replaced by new node.";
+    }
+
+
+    @Test(dependsOnMethods = "testIfBranch")
+    public void testReplaceConditionNode()
+    {
+        Node node = new IfThenElse(new Constant(1), new Constant(2), new Constant(3));
+        Node newNode = node.replaceNode(1, new Constant(0));
+        assert newNode instanceof IfThenElse : "Replacing condition node should not change type of root node.";
+        assert newNode.evaluate(BinaryNode.NO_ARGS) == 3d : "Changing condition node should change evaluation.";
+    }
+
+
+    @Test(dependsOnMethods = "testIfBranch")
+    public void testReplaceThenNode()
+    {
+        Node node = new IfThenElse(new Constant(1), new Constant(2), new Constant(3));
+        Node newNode = node.replaceNode(2, new Constant(4));
+        assert newNode instanceof IfThenElse : "Replacing then node should not change type of root node.";
+        assert newNode.evaluate(BinaryNode.NO_ARGS) == 4d : "Changing then node should change evaluation.";
+    }
+
+
+    @Test(dependsOnMethods = "testElseBranch")
+    public void testReplaceElseNode()
+    {
+        Node node = new IfThenElse(new Constant(0), new Constant(2), new Constant(3));
+        Node newNode = node.replaceNode(3, new Constant(5));
+        assert newNode instanceof IfThenElse : "Replacing else node should not change type of root node.";
+        assert newNode.evaluate(BinaryNode.NO_ARGS) == 5d : "Changing then node should change evaluation.";
+    }
+
+
+    /**
+     * Test replacing of nodes which are not direct sub-nodes of this node but are further down
+     * the tree.
+     */
+    @Test(dependsOnMethods = "testReplaceElseNode")
+    public void testReplaceSubNodes()
+    {
+        Node node = new IfThenElse(new Constant(0), new Constant(2), new Addition(new Constant(3), new Constant(4)));
+        // Replace both of the constants summed by the addition node on the else branch.
+        Node newNode = node.replaceNode(4, new Constant(5));
+        newNode = newNode.replaceNode(5, new Constant(6));
+        assert newNode instanceof IfThenElse : "Replacing sub-nodes should not change type of root node.";
+        assert newNode.evaluate(BinaryNode.NO_ARGS) == 11d : "Changing sub-nodes should change evaluation.";
+    }
+
+
+    @Test
+    public void testZeroProbabilityMutation()
+    {
+        Node node = new IfThenElse(new Constant(0), new Constant(2), new Addition(new Constant(3), new Constant(4)));
+        double value = node.evaluate(BinaryNode.NO_ARGS);
+        String string = node.print();
+
+        Node mutated = node.mutate(ExamplesTestUtils.getRNG(), Probability.ZERO, null);
+        assert mutated == node : "Node should not have changed.";
+        assert value == mutated.evaluate(BinaryNode.NO_ARGS) : "Node should not have been altered.";
+        assert string.equals(mutated.print()) : "Node should not have been altered.";
+    }
+
+
+    @Test
+    public void testSimplify()
+    {
+        Node node = new IfThenElse(new Constant(0), new Constant(1), new Constant(2));
+        Node simplified = node.simplify();
+        assert simplified instanceof Constant
+            : "Simplified node should be Constant, is " + simplified.getClass().getSimpleName();
+        assert simplified.evaluate(BinaryNode.NO_ARGS) == node.evaluate(BinaryNode.NO_ARGS) : "Simplified answer differs.";
+    }
+
+
+    /**
+     * Make sure that sub-nodes are simplified.
+     */
+    @Test
+    public void testSimplifySubNode()
+    {
+        Node node = new IfThenElse(new Constant(4),
+                                   new IfThenElse(new Constant(1), new Constant(2), new Constant(3)),
+                                   new Constant(5));
+        Node simplified = node.simplify();
+        assert simplified instanceof Constant
+            : "Simplified node should be Constant, is " + simplified.getClass().getSimpleName();
+        assert simplified.evaluate(BinaryNode.NO_ARGS) == node.evaluate(BinaryNode.NO_ARGS) : "Simplified answer differs.";
+        assert simplified.evaluate(BinaryNode.NO_ARGS) == 2;
+    }
+
+
+    /**
+     * Make sure that sub-nodes are simplified and that these simplfications are taken into
+     * account when optimising the parent node (in other words the child nodes should be
+     * simplified first).
+     */
+    @Test
+    public void testSimplifyComplex()
+    {
+        Node node = new IfThenElse(new IfThenElse(new Constant(1), new Constant(2), new Constant(3)),
+                                   new Constant(4),
+                                   new Constant(5));
+        Node simplified = node.simplify();
+        // It is not sufficient to simplify this to an IfThenElse with a constant for each node,
+        // the fact that the condition node can be replaced by a Constant should result in the whole
+        // tree being reduced to a single constant (with a value of 4).
+        assert simplified instanceof Constant
+            : "Simplified node should be Constant, is " + simplified.getClass().getSimpleName();
+        assert simplified.evaluate(BinaryNode.NO_ARGS) == node.evaluate(BinaryNode.NO_ARGS) : "Simplified answer differs.";
+        assert simplified.evaluate(BinaryNode.NO_ARGS) == 4;
+    }
+
+
+    /**
+     * Test that simplification doesn't cause any problems when the expression is already as simple
+     * as possible.
+     */
+    @Test
+    public void testSimplifySimplest()
+    {
+        Node node = new IfThenElse(new Parameter(0), new Constant(1), new Constant(2));
+        Node simplified = node.simplify();
+        assert simplified == node : "Expression should not have been changed.";
+    }
+
+
+    /**
+     * If the two branches (then and else) are identical, it doesn't matter what the condition is,
+     * the tree can be replaced by either one of the branches.
+     */
+    @Test
+    public void testSimplifyIdenticalBranches()
+    {
+        Node node = new IfThenElse(new Parameter(0),
+                                   new Constant(2),
+                                   new Constant(2));
+        Node simplified = node.simplify();
+        assert simplified instanceof Constant
+            : "Simplified node should be Constant, is " + simplified.getClass().getSimpleName();
+        double[] args = new double[]{1}; // Need one argument for the parameter node to use.
+        assert simplified.evaluate(args) == node.evaluate(args) : "Simplified answer differs.";
+        assert simplified.evaluate(args) == 2;
+
+    }
+}
diff --git a/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/geneticprogramming/IsGreaterTest.java b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/geneticprogramming/IsGreaterTest.java
new file mode 100644
index 0000000..91baeec
--- /dev/null
+++ b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/geneticprogramming/IsGreaterTest.java
@@ -0,0 +1,110 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.geneticprogramming;
+
+import org.testng.annotations.Test;
+
+/**
+ * Simple unit test for the {@link IsGreater} node type.
+ * @author Daniel Dyer
+ */
+public class IsGreaterTest
+{
+    /**
+     * If two nodes are equal then neither is greater than the other.
+     */
+    @Test
+    public void testBothNodesEqual()
+    {
+        Node node = new IsGreater(new Constant(1), new Constant(1));
+        assert node.evaluate(new double[0]) == 0 : "First node should not be greater than second.";
+    }
+
+
+    @Test
+    public void testFirstNodeGreater()
+    {
+        Node node = new IsGreater(new Constant(2), new Constant(1));
+        assert node.evaluate(new double[0]) > 0 : "First node should be greater than second.";
+    }
+
+
+    @Test
+    public void testSecondNodeGreater()
+    {
+        Node node = new IsGreater(new Constant(-1), new Constant(1));
+        assert node.evaluate(new double[0]) == 0 : "First node should be less than second.";
+    }
+
+
+    /**
+     * If the arguments to the IsGreater function are both constants then the node
+     * should be replaced by a constant node containing the evaluation of this expression.
+     */
+    @Test
+    public void testSimplifyConstants()
+    {
+        Node node = new IsGreater(new Constant(7), new Constant(5));
+        Node simplified = node.simplify();
+        assert simplified instanceof Constant
+            : "Simplified node should be Constant, is " + simplified.getClass().getSimpleName();
+        assert simplified.evaluate(BinaryNode.NO_ARGS) == node.evaluate(BinaryNode.NO_ARGS) : "Simplified answer differs.";
+        assert simplified.evaluate(BinaryNode.NO_ARGS) == 1;
+
+    }
+
+
+    @Test
+    public void testSimplifyIdenticalArguments()
+    {
+        Node node = new IsGreater(new Parameter(0), new Parameter(0));
+        Node simplified = node.simplify();
+        assert simplified instanceof Constant
+            : "Simplified node should be Constant, is " + simplified.getClass().getSimpleName();
+        double[] args = new double[]{5}; // Provides a value for the parameter nodes.
+        assert simplified.evaluate(args) == node.evaluate(args) : "Simplified answer differs.";
+    }
+
+    
+    /**
+     * Test that simplification doesn't cause any problems when the expression is already as simple
+     * as possible.
+     */
+    @Test
+    public void testSimplifySimplest()
+    {
+        Node node = new IsGreater(new Parameter(0), new Constant(1));
+        Node simplified = node.simplify();
+        assert simplified == node : "Expression should not have been changed.";
+    }
+
+
+    /**
+     * Make sure that sub-nodes are simplified.
+     */
+    @Test
+    public void testSimplifySubNode()
+    {
+        Node node = new IsGreater(new Parameter(0),
+                                  new IsGreater(new Constant(3), new Constant(2)));
+        Node simplified = node.simplify();
+        assert simplified instanceof IsGreater
+            : "Simplified node should be IsGreater, is " + simplified.getClass().getSimpleName();
+        double[] args = new double[]{5}; // Provides a value for the parameter nodes.
+        assert simplified.evaluate(args) == node.evaluate(args) : "Simplified answer differs.";
+        assert simplified.countNodes() < node.countNodes() : "Should be fewer nodes after simplification.";
+    }
+}
diff --git a/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/geneticprogramming/MultiplicationTest.java b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/geneticprogramming/MultiplicationTest.java
new file mode 100644
index 0000000..f81c367
--- /dev/null
+++ b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/geneticprogramming/MultiplicationTest.java
@@ -0,0 +1,157 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.geneticprogramming;
+
+import org.testng.annotations.Test;
+
+/**
+ * Simple unit test for the {@link Multiplication} node type.
+ * @author Daniel Dyer
+ */
+public class MultiplicationTest
+{
+    @Test
+    public void testEvaluation()
+    {
+        Node node = new Multiplication(new Constant(5), new Constant(2));
+        double value = node.evaluate(new double[0]);
+        assert value == 10 : "Wrong result: " + value;
+    }
+
+
+    @Test
+    public void testStringRepresentation()
+    {
+        Node node = new Multiplication(new Constant(5), new Parameter(0));
+        assert node.print().equals("(5.0 * arg0)") : "Wrong string representation: " + node.print();
+    }
+
+
+    /**
+     * If the arguments to the multiply function are both constants then the multiplication node
+     * should be replaced by a constant node containing the evaluation of this product.
+     */
+    @Test
+    public void testSimplifyConstants()
+    {
+        Node node = new Multiplication(new Constant(3), new Constant(4));
+        Node simplified = node.simplify();
+        assert simplified instanceof Constant
+            : "Simplified node should be Constant, is " + simplified.getClass().getSimpleName();
+        assert simplified.evaluate(BinaryNode.NO_ARGS) == node.evaluate(BinaryNode.NO_ARGS) : "Simplified answer differs.";
+        assert simplified.evaluate(BinaryNode.NO_ARGS) == 12;
+
+    }
+
+
+    /**
+     * If the lefthand argument is zero, the result will always be zero regardless of the righthand
+     * argument.
+     */
+    @Test
+    public void testSimplifyMultiplyZero()
+    {
+        Node node = new Multiplication(new Constant(0), new Parameter(0));
+        Node simplified = node.simplify();
+        assert simplified instanceof Constant
+            : "Simplified node should be Constant, is " + simplified.getClass().getSimpleName();
+        double[] args = new double[]{5}; // Provides a value for the parameter nodes.
+        assert simplified.evaluate(args) == node.evaluate(args) : "Simplified answer differs.";
+        assert simplified.evaluate(BinaryNode.NO_ARGS) == 0;
+
+    }
+
+
+    /**
+     * If the righthand argument is zero, the result will always be zero regardless of the lefthand
+     * argument.
+     */
+    @Test
+    public void testSimplifyMultiplyByZero()
+    {
+        Node node = new Multiplication(new Parameter(0), new Constant(0));
+        Node simplified = node.simplify();
+        assert simplified instanceof Constant
+            : "Simplified node should be Constant, is " + simplified.getClass().getSimpleName();
+        double[] args = new double[]{5}; // Provides a value for the parameter nodes.
+        assert simplified.evaluate(args) == node.evaluate(args) : "Simplified answer differs.";
+        assert simplified.evaluate(BinaryNode.NO_ARGS) == 0;
+    }
+
+
+    /**
+     * If the lefthand argument is one, the result can be reduced to the righthand argument.
+     */
+    @Test
+    public void testSimplifyMultiplyOne()
+    {
+        Node node = new Multiplication(new Constant(1), new Parameter(0));
+        Node simplified = node.simplify();
+        assert simplified instanceof Parameter
+            : "Simplified node should be Parameter, is " + simplified.getClass().getSimpleName();
+        double[] args = new double[]{5}; // Provides a value for the parameter nodes.
+        assert simplified.evaluate(args) == node.evaluate(args) : "Simplified answer differs.";
+        assert simplified.evaluate(args) == 5;
+
+    }
+
+
+    /**
+     * If the righthand argument is one, the result can be reduced to the lefthand argument.
+     */
+    @Test
+    public void testSimplifyMultiplyByOne()
+    {
+        Node node = new Multiplication(new Parameter(0), new Constant(1));
+        Node simplified = node.simplify();
+        assert simplified instanceof Parameter
+            : "Simplified node should be Parameter, is " + simplified.getClass().getSimpleName();
+        double[] args = new double[]{5}; // Provides a value for the parameter nodes.
+        assert simplified.evaluate(args) == node.evaluate(args) : "Simplified answer differs.";
+        assert simplified.evaluate(args) == 5;
+    }
+
+
+    /**
+     * Test that simplification doesn't cause any problems when the expression is already as simple
+     * as possible.
+     */
+    @Test
+    public void testSimplifySimplest()
+    {
+        Node node = new Multiplication(new Parameter(0), new Constant(2));
+        Node simplified = node.simplify();
+        assert simplified == node : "Expression should not have been changed.";
+    }
+
+
+    /**
+     * Make sure that sub-nodes are simplified.
+     */
+    @Test
+    public void testSimplifySubNode()
+    {
+        Node node = new Multiplication(new Parameter(0),
+                                       new Multiplication(new Constant(3), new Constant(2)));
+        Node simplified = node.simplify();
+        assert simplified instanceof Multiplication
+            : "Simplified node should be Multiplication, is " + simplified.getClass().getSimpleName();
+        double[] args = new double[]{5}; // Provides a value for the parameter nodes.
+        assert simplified.evaluate(args) == node.evaluate(args) : "Simplified answer differs.";
+        assert simplified.countNodes() < node.countNodes() : "Should be fewer nodes after simplification.";
+    }
+
+}
diff --git a/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/geneticprogramming/ParameterTest.java b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/geneticprogramming/ParameterTest.java
new file mode 100644
index 0000000..7324242
--- /dev/null
+++ b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/geneticprogramming/ParameterTest.java
@@ -0,0 +1,60 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.geneticprogramming;
+
+import org.testng.annotations.Test;
+
+/**
+ * Simple unit test for the {@link Parameter} node type.
+ * @author Daniel Dyer
+ */
+public class ParameterTest
+{
+    @Test
+    public void testParameterSelection()
+    {
+        Parameter parameter = new Parameter(2);
+        double value = parameter.evaluate(new double[]{0, 1, 2, 3});
+        assert value == 2 : "Incorect argument selected: " + value;
+    }
+
+
+    @Test(expectedExceptions = IllegalArgumentException.class)
+    public void testInvalidParameterSelection()
+    {
+        Parameter parameter = new Parameter(2);
+        // There is only one argument, so trying to select the 3rd one should
+        // result in an IllegalArgumentException.
+        parameter.evaluate(new double[]{0});
+    }
+
+
+    @Test
+    public void testEquality()
+    {
+        Parameter zero = new Parameter(0);
+        Parameter one = new Parameter(1);
+        Parameter anotherOne = new Parameter(1);
+
+        assert zero.equals(zero) : "Equality must be reflexive.";
+        assert one.equals(anotherOne) : "Same-index parameters must be equal.";
+        assert anotherOne.equals(one) : "Equality must be symmetric.";
+        assert one.hashCode() == anotherOne.hashCode() : "Equal objects must have equal hash codes.";
+        assert !zero.equals(one) : "Different index parameters must be non-equal.";
+        assert !zero.equals(null) : "No non-null object should not be considered equal to null.";
+        assert !zero.equals(Integer.valueOf(0)) : "Objects of different types should not be equal.";
+    }
+}
diff --git a/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/geneticprogramming/SimplificationTest.java b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/geneticprogramming/SimplificationTest.java
new file mode 100644
index 0000000..f439021
--- /dev/null
+++ b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/geneticprogramming/SimplificationTest.java
@@ -0,0 +1,70 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.geneticprogramming;
+
+import java.util.Arrays;
+import java.util.List;
+import org.testng.annotations.Test;
+import org.uncommons.maths.random.Probability;
+import org.uncommons.watchmaker.examples.ExamplesTestUtils;
+
+/**
+ * Unit test for the {@link Simplification} evolutionary operator.
+ * @author Daniel Dyer
+ */
+public class SimplificationTest
+{
+    /**
+     * When the probability is 1, all candidates should be processed.
+     */
+    @Test
+    public void testProbabilityOne()
+    {
+        Node node1 = new Addition(new Constant(1), new Constant(1));
+        Node node2 = new Subtraction(new Constant(5), new Constant(4));
+        Node node3 = new Multiplication(new Constant(3), new Constant(3));
+        List<Node> population = Arrays.asList(node1, node2, node3); 
+
+        Simplification simplification = new Simplification();
+        List<Node> evolved = simplification.apply(population, ExamplesTestUtils.getRNG());
+        assert evolved.size() == population.size() : "Output should be same size as input.";
+        for (Node node : evolved)
+        {
+            assert node instanceof Constant : "Node was not simplified.";
+        }
+    }
+
+
+    /**
+     * When the probability is 0, no candidates should be processed.
+     */
+    @Test
+    public void testProbabilityZero()
+    {
+        Node node1 = new Addition(new Constant(1), new Constant(1));
+        Node node2 = new Subtraction(new Constant(5), new Constant(4));
+        Node node3 = new Multiplication(new Constant(3), new Constant(3));
+        List<Node> population = Arrays.asList(node1, node2, node3);
+
+        Simplification simplification = new Simplification(Probability.ZERO);
+        List<Node> evolved = simplification.apply(population, ExamplesTestUtils.getRNG());
+        assert evolved.size() == population.size() : "Output should be same size as input.";
+        for (Node node : evolved)
+        {
+            assert !(node instanceof Constant) : "Node should not have been simplified.";
+        }
+    }
+}
diff --git a/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/geneticprogramming/SubtractionTest.java b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/geneticprogramming/SubtractionTest.java
new file mode 100644
index 0000000..1682b25
--- /dev/null
+++ b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/geneticprogramming/SubtractionTest.java
@@ -0,0 +1,133 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.geneticprogramming;
+
+import org.testng.annotations.Test;
+
+/**
+ * Simple unit test for the {@link Subtraction} node type.
+ * @author Daniel Dyer
+ */
+public class SubtractionTest
+{
+    @Test
+    public void testEvaluation()
+    {
+        Node node = new Subtraction(new Constant(7), new Constant(3));
+        double value = node.evaluate(new double[0]);
+        assert value == 4 : "Wrong result: " + value;
+    }
+
+    
+    @Test
+    public void testStringRepresentation()
+    {
+        Node node = new Subtraction(new Constant(7), new Constant(3));
+        assert node.print().equals("(7.0 - 3.0)") : "Wrong string representation: " + node.print();
+    }
+
+
+    /**
+     * If the arguments to the subtract function are both constants then the subtract node
+     * should be replaced by a constant node containing the evaluation of this sum.
+     */
+    @Test
+    public void testSimplifyConstants()
+    {
+        Node node = new Subtraction(new Constant(7), new Constant(5));
+        Node simplified = node.simplify();
+        assert simplified instanceof Constant
+            : "Simplified node should be Constant, is " + simplified.getClass().getSimpleName();
+        assert simplified.evaluate(BinaryNode.NO_ARGS) == node.evaluate(BinaryNode.NO_ARGS) : "Simplified answer differs.";
+        assert simplified.evaluate(BinaryNode.NO_ARGS) == 2;
+    }
+
+
+    /**
+     * If the arguments to the subtract function are identical, even if they are not constant,
+     * then the answer will always be zero, so this node should be replaced by the constant zero.
+     */
+    @Test
+    public void testSimplifyIdenticalArguments()
+    {
+        Node node = new Subtraction(new Parameter(0), new Parameter(0));
+        Node simplified = node.simplify();
+        assert simplified instanceof Constant
+            : "Simplified node should be Constant, is " + simplified.getClass().getSimpleName();
+        double[] args = new double[]{5}; // Provides a value for the parameter nodes.
+        assert simplified.evaluate(args) == node.evaluate(args) : "Simplified answer differs.";
+        assert simplified.evaluate(args) == 0;
+    }
+
+
+    /**
+     * Test that simplification doesn't cause any problems when the expression is already as simple
+     * as possible.
+     */
+    @Test
+    public void testSimplifySimplest()
+    {
+        Node node = new Subtraction(new Parameter(0), new Constant(1));
+        Node simplified = node.simplify();
+        assert simplified == node : "Expression should not have been changed.";
+    }
+
+
+    /**
+     * If the second argument is zero, the experession can be replaced by its lefthand side.
+     */
+    @Test
+    public void testSimplifySubtractZero()
+    {
+        Node node = new Subtraction(new Parameter(0), new Constant(0));
+        Node simplified = node.simplify();
+        assert simplified instanceof Parameter
+            : "Simplified node should be Parameter, is " + simplified.getClass().getSimpleName();
+        double[] args = new double[]{5}; // Provides a value for the parameter nodes.
+        assert simplified.evaluate(args) == node.evaluate(args) : "Simplified answer differs.";
+        assert simplified.evaluate(args) == 5;
+    }
+
+
+    /**
+     * But if the first argument is zero, the experession should not be simplified as it has
+     * the effect of negating the second argument.
+     */
+    @Test
+    public void testSimplifySubtractFromZero()
+    {
+        Node node = new Subtraction(new Constant(0), new Parameter(0));
+        Node simplified = node.simplify();
+        assert simplified == node : "Expression should not have been changed.";
+    }
+
+
+    /**
+     * Make sure that sub-nodes are simplified.
+     */
+    @Test
+    public void testSimplifySubNode()
+    {
+        Node node = new Subtraction(new Parameter(0),
+                                    new Subtraction(new Constant(3), new Constant(2)));
+        Node simplified = node.simplify();
+        assert simplified instanceof Subtraction
+            : "Simplified node should be Subtraction, is " + simplified.getClass().getSimpleName();
+        double[] args = new double[]{5}; // Provides a value for the parameter nodes.
+        assert simplified.evaluate(args) == node.evaluate(args) : "Simplified answer differs.";
+        assert simplified.countNodes() < node.countNodes() : "Should be fewer nodes after simplification.";
+    }
+}
diff --git a/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/geneticprogramming/SwingGPTreeRendererTest.java b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/geneticprogramming/SwingGPTreeRendererTest.java
new file mode 100644
index 0000000..c0ac452
--- /dev/null
+++ b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/geneticprogramming/SwingGPTreeRendererTest.java
@@ -0,0 +1,51 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.geneticprogramming;
+
+import java.awt.Dimension;
+import javax.swing.JComponent;
+import org.testng.annotations.Test;
+
+/**
+ * Basic unit test for the {@link SwingGPTreeRenderer} class.
+ * @author Daniel Dyer
+ */
+public class SwingGPTreeRendererTest
+{
+    // There's not much we can effectively test for this class, but we can at least
+    // make sure the generated component has the correct dimensions.
+    @Test
+    public void testSizes()
+    {
+        SwingGPTreeRenderer renderer = new SwingGPTreeRenderer();
+
+        // Simple case.
+        Node tree = new Constant(2);
+        JComponent component = renderer.render(tree);
+        Dimension minSize = component.getMinimumSize();
+        assert minSize.width == 30 : "Wrong width: " + minSize.width;
+        assert minSize.height == 50 : "Wrong height: " + minSize.height;
+
+        // More complicated case.
+        tree = new IfThenElse(new Parameter(0),
+                              new Addition(new Constant(2), new Parameter(1)),
+                              new Constant(5));
+        component = renderer.render(tree);
+        minSize = component.getMinimumSize();
+        assert minSize.width == 120 : "Wrong width: " + minSize.width;
+        assert minSize.height == 150 : "Wrong height: " + minSize.height;
+    }
+}
diff --git a/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/geneticprogramming/TreeCrossoverTest.java b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/geneticprogramming/TreeCrossoverTest.java
new file mode 100644
index 0000000..5fdf777
--- /dev/null
+++ b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/geneticprogramming/TreeCrossoverTest.java
@@ -0,0 +1,47 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.geneticprogramming;
+
+import java.util.Arrays;
+import java.util.List;
+import org.testng.annotations.Test;
+import org.uncommons.watchmaker.examples.ExamplesTestUtils;
+
+/**
+ * Unit test for the {@link TreeCrossover} evolutionary operator used by
+ * the genetic programming example application.
+ * @author Daniel Dyer
+ */
+public class TreeCrossoverTest
+{
+    /**
+     * This is just a simple sanity check.  Cross-over should result in the same
+     * number of individuals, all constructed from the same set of nodes that existed
+     * in the parent generation (but perhaps connected differently).
+     */
+    @Test
+    public void testCrossover()
+    {
+        TreeCrossover crossover = new TreeCrossover();
+        Node tree1 = new Multiplication(new Constant(1), new Constant(2));
+        Node tree2 = new Subtraction(new Parameter(0), new Parameter(1));
+
+        List<Node> offspring = crossover.apply(Arrays.asList(tree1, tree2), ExamplesTestUtils.getRNG());
+        assert offspring.size() == 2 : "Should be 2 offspring after cross-over.";
+        int totalNodeCount = offspring.get(0).countNodes() + offspring.get(1).countNodes();
+        assert totalNodeCount == 6 : "Should be exactly 6 nodes in total, is " + totalNodeCount; 
+    }
+}
diff --git a/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/geneticprogramming/TreeEvaluatorTest.java b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/geneticprogramming/TreeEvaluatorTest.java
new file mode 100644
index 0000000..7aec257
--- /dev/null
+++ b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/geneticprogramming/TreeEvaluatorTest.java
@@ -0,0 +1,78 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.geneticprogramming;
+
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.Map;
+import org.testng.annotations.Test;
+import org.uncommons.watchmaker.framework.FitnessEvaluator;
+
+/**
+ * Unit test for the {@link FitnessEvaluator} used
+ * in the genetic programming example applicaiton.
+ * @author Daniel Dyer
+ */
+public class TreeEvaluatorTest
+{
+    /**
+     * A function that perfectly generates the correct output for all inputs
+     * should have a fitness of zero.
+     */
+    @Test
+    public void testPerfectFunction()
+    {
+        Map<double[], Double> data = new HashMap<double[], Double>();
+        // Data for multiplication program.
+        data.put(new double[]{5d, 3d}, 15d);
+        data.put(new double[]{3d, 8d}, 24d);
+        data.put(new double[]{7d, 2d}, 14d);
+
+        FitnessEvaluator<Node> evaluator = new TreeEvaluator(data);
+
+        // Program that multiplies its two inputs together.
+        Node program = new Multiplication(new Parameter(0), new Parameter(1));
+
+        double fitness = evaluator.getFitness(program, Arrays.asList(program));
+        assert fitness == 0 : "Correct program should have zero fitness.";
+    }
+
+
+    /**
+     * A function that doesn't generate the correct output for all inputs
+     * should have a non-zero fitness.
+     */
+    @Test
+    public void testIncorrectFunction()
+    {
+        Map<double[], Double> data = new HashMap<double[], Double>();
+        // Data for multiplication program.
+        data.put(new double[]{5d, 3d}, 15d);
+        data.put(new double[]{3d, 8d}, 24d);
+        data.put(new double[]{7d, 2d}, 14d);
+
+        FitnessEvaluator<Node> evaluator = new TreeEvaluator(data);
+
+        // Program that multiplies its first input by 3 (will give the correct answer
+        // for the first set of inputs but the wrong answer for the other two).
+        Node program = new Multiplication(new Parameter(0), new Constant(3d));
+
+        double fitness = evaluator.getFitness(program, Arrays.asList(program));
+        // Error on second example is 15, error on third is 7.
+        // 15^2 + 7^2 = 225 + 49 = 274
+        assert fitness == 274d : "Wrong fitness for incorrect program.";
+    }
+}
diff --git a/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/geneticprogramming/TreeFactoryTest.java b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/geneticprogramming/TreeFactoryTest.java
new file mode 100644
index 0000000..d4ed9e6
--- /dev/null
+++ b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/geneticprogramming/TreeFactoryTest.java
@@ -0,0 +1,66 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.geneticprogramming;
+
+import java.util.List;
+import org.testng.annotations.Test;
+import org.uncommons.maths.random.Probability;
+import org.uncommons.watchmaker.examples.ExamplesTestUtils;
+import org.uncommons.watchmaker.framework.CandidateFactory;
+
+/**
+ * Unit test for the {@link TreeFactory} used by the gentic programming
+ * example.
+ * @author Daniel Dyer
+ */
+public class TreeFactoryTest
+{
+    @Test
+    public void testMaxDepth()
+    {
+        final int maxDepth = 3;
+        CandidateFactory<Node> factory = new TreeFactory(2,
+                                                         maxDepth,
+                                                         new Probability(0.6),
+                                                         Probability.EVENS);
+        List<Node> trees = factory.generateInitialPopulation(20, ExamplesTestUtils.getRNG());
+        for (Node tree : trees)
+        {
+            // Make sure that each tree is no bigger than the maximum permitted.
+            assert tree.getDepth() <= maxDepth : "Generated tree is too deep: " + tree.getDepth();
+        }
+    }
+
+
+    @Test(expectedExceptions = IllegalArgumentException.class)
+    public void testInvalidParameterCount()
+    {
+        new TreeFactory(-1,
+                        1,
+                        Probability.EVENS,
+                        Probability.EVENS); // Should throw an exception, parameter count can't be negative.
+    }
+
+    
+    @Test(expectedExceptions = IllegalArgumentException.class)
+    public void testInvalidMaxDepth()
+    {
+        new TreeFactory(1,
+                        0,
+                        Probability.EVENS,
+                        Probability.EVENS); // Should throw an exception, depth must be at least one.
+    }
+}
diff --git a/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/geneticprogramming/TreeMutationTest.java b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/geneticprogramming/TreeMutationTest.java
new file mode 100644
index 0000000..3bf6b0f
--- /dev/null
+++ b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/geneticprogramming/TreeMutationTest.java
@@ -0,0 +1,76 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.geneticprogramming;
+
+import java.util.Arrays;
+import java.util.IdentityHashMap;
+import java.util.List;
+import java.util.Map;
+import org.testng.annotations.Test;
+import org.uncommons.maths.random.Probability;
+import org.uncommons.watchmaker.examples.ExamplesTestUtils;
+import org.uncommons.watchmaker.framework.EvolutionaryOperator;
+
+/**
+ * Unit test for the {@link TreeMutation} evolutionary operator.
+ * @author Daniel Dyer
+ */
+public class TreeMutationTest
+{
+    /**
+     * If the mutation doesn't happen, the candidates should be returned unaltered. 
+     */
+    @Test
+    public void testNoMutations()
+    {
+        TreeFactory treeFactory = new TreeFactory(0, 3, Probability.EVENS, Probability.EVENS);
+        EvolutionaryOperator<Node> mutation = new TreeMutation(treeFactory,
+                                                               Probability.ZERO); // Zero probability means no mutations.
+        List<Node> candidates = Arrays.<Node>asList(new Addition(new Constant(3), new Constant(4)));
+        List<Node> result = mutation.apply(candidates, ExamplesTestUtils.getRNG());
+        assert result.size() == 1 : "Wrong number of trees returned: " + result.size();
+        assert candidates.get(0) == result.get(0) : "Tree should have been returned unmodified.";
+    }
+
+
+    /**
+     * If the mutation doesn't happen, the candidates should be returned unaltered.
+     */
+    @Test
+    public void testSomeMutations()
+    {
+        TreeFactory treeFactory = new TreeFactory(1, 4, new Probability(0.6d), new Probability(0.2d));
+        EvolutionaryOperator<Node> mutation = new TreeMutation(treeFactory,
+                                                               Probability.ONE); // Probability of 1 means guaranteed mutations.
+        List<Node> candidates = treeFactory.generateInitialPopulation(20, ExamplesTestUtils.getRNG());
+
+        Map<Node, Node> distinctTrees = new IdentityHashMap<Node, Node>();
+        for (Node node : candidates)
+        {
+            distinctTrees.put(node, node);
+        }
+
+        List<Node> result = mutation.apply(candidates, ExamplesTestUtils.getRNG());
+        assert result.size() == 20 : "Wrong number of trees returned: " + result.size();
+        for (Node node : result)
+        {
+            distinctTrees.put(node, node);
+        }
+        
+        // If none of the original trees are returned, we should have 40 distict trees.
+        assert distinctTrees.size() == 40 : "New trees should have been returned.";
+    }
+}
diff --git a/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/monalisa/AddPolygonMutationTest.java b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/monalisa/AddPolygonMutationTest.java
new file mode 100644
index 0000000..53c7aea
--- /dev/null
+++ b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/monalisa/AddPolygonMutationTest.java
@@ -0,0 +1,104 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.monalisa;
+
+import java.awt.Dimension;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import org.testng.annotations.Test;
+import org.uncommons.maths.random.Probability;
+import org.uncommons.watchmaker.examples.ExamplesTestUtils;
+import org.uncommons.watchmaker.framework.EvolutionaryOperator;
+
+/**
+ * Unit test for the {@link AddPolygonMutation} evolutionary operator.
+ * @author Daniel Dyer
+ */
+public class AddPolygonMutationTest
+{
+    private final PolygonImageFactory factory = new PolygonImageFactory(new Dimension(200, 200));
+
+    @Test
+    public void testAddPolygon()
+    {
+        List<ColouredPolygon> image = factory.generateRandomCandidate(ExamplesTestUtils.getRNG());
+        assert image.size() == 2 : "Image should have 2 polygons";
+        List<List<ColouredPolygon>> list = new ArrayList<List<ColouredPolygon>>(1);
+        list.add(image);
+
+        EvolutionaryOperator<List<ColouredPolygon>> mutation = new AddPolygonMutation(Probability.ONE,
+                                                                                      factory,
+                                                                                      5);
+
+        List<List<ColouredPolygon>> evolved = mutation.apply(list, ExamplesTestUtils.getRNG());
+        assert evolved.size() == 1 : "Population size should not be altered by mutation.";
+        assert evolved.get(0).size() == image.size() + 1 : "Image should have 1 extra polygon after mutation.";
+    }
+
+
+    @Test
+    public void testZeroProbability()
+    {
+        List<ColouredPolygon> image = factory.generateRandomCandidate(ExamplesTestUtils.getRNG());
+        assert image.size() == 2 : "Image should have 2 polygons";
+        List<List<ColouredPolygon>> list = new ArrayList<List<ColouredPolygon>>(1);
+        list.add(image);
+
+        EvolutionaryOperator<List<ColouredPolygon>> mutation = new AddPolygonMutation(Probability.ZERO,
+                                                                                      factory,
+                                                                                      5);
+
+        List<List<ColouredPolygon>> evolved = mutation.apply(list, ExamplesTestUtils.getRNG());
+        assert evolved.size() == 1 : "Population size should not be altered by mutation.";
+        assert evolved.get(0).size() == image.size() : "Image should have same number of polygons.";
+        assert evolved.get(0) == image : "Image should not have been changed at all.";
+    }
+
+
+    /**
+     * If the image already has the maximum permitted number of polygons, extra polygons
+     * should not be added by mutation.
+     */
+    @Test
+    public void testAddMaxPolygons()
+    {
+        List<ColouredPolygon> image = Arrays.asList(factory.createRandomPolygon(ExamplesTestUtils.getRNG()),
+                                                    factory.createRandomPolygon(ExamplesTestUtils.getRNG()),
+                                                    factory.createRandomPolygon(ExamplesTestUtils.getRNG()));
+        List<List<ColouredPolygon>> list = new ArrayList<List<ColouredPolygon>>(1);
+        list.add(image);
+
+        EvolutionaryOperator<List<ColouredPolygon>> mutation = new AddPolygonMutation(Probability.ONE,
+                                                                                      factory,
+                                                                                      3);
+
+        List<List<ColouredPolygon>> evolved = mutation.apply(list, ExamplesTestUtils.getRNG());
+        assert evolved.size() == 1 : "Population size should not be altered by mutation.";
+        assert evolved.get(0).size() == image.size() : "Image should have no more than the maximum number of polygons.";
+        assert evolved.get(0) == image : "Image should not have been changed at all.";
+    }
+
+
+    /**
+     * An image must have at least 2 polygons.  The configured maximum must respect this.
+     */
+    @Test(expectedExceptions = IllegalArgumentException.class)
+    public void testInvalidMaximum()
+    {
+        new AddPolygonMutation(Probability.ONE, factory, 1); // Invalid, should throw IllegalArgumentException.
+    }
+}
diff --git a/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/monalisa/AddVertexMutationTest.java b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/monalisa/AddVertexMutationTest.java
new file mode 100644
index 0000000..50579a8
--- /dev/null
+++ b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/monalisa/AddVertexMutationTest.java
@@ -0,0 +1,100 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.monalisa;
+
+import java.awt.Color;
+import java.awt.Dimension;
+import java.awt.Point;
+import java.util.ArrayList;
+import java.util.List;
+import org.testng.annotations.Test;
+import org.uncommons.maths.random.Probability;
+import org.uncommons.watchmaker.examples.ExamplesTestUtils;
+import org.uncommons.watchmaker.framework.EvolutionaryOperator;
+
+/**
+ * Unit test for the {@link AddVertexMutation} evolutionary operator.
+ * @author Daniel Dyer
+ */
+public class AddVertexMutationTest
+{
+    private final Dimension canvasSize = new Dimension(200, 200);
+    private final PolygonImageFactory factory = new PolygonImageFactory(canvasSize);
+
+    @Test
+    public void testAddVertex()
+    {
+        ColouredPolygon polygon = factory.createRandomPolygon(ExamplesTestUtils.getRNG());
+        List<ColouredPolygon> image = new ArrayList<ColouredPolygon>(1);
+        image.add(polygon);
+
+        EvolutionaryOperator<ColouredPolygon> mutation = new AddVertexMutation(canvasSize,
+                                                                               Probability.ONE);
+
+        List<ColouredPolygon> evolved = mutation.apply(image, ExamplesTestUtils.getRNG());
+        assert evolved.size() == 1 : "Polygon count should not be altered by mutation.";
+        List<Point> vertices = evolved.get(0).getVertices();
+        assert vertices.size() == polygon.getVertices().size() + 1
+            : "Polygon should have 1 extra point after mutation.";
+    }
+
+
+    @Test
+    public void testZeroProbability()
+    {
+        ColouredPolygon polygon = factory.createRandomPolygon(ExamplesTestUtils.getRNG());
+        List<ColouredPolygon> image = new ArrayList<ColouredPolygon>(1);
+        image.add(polygon);
+
+        EvolutionaryOperator<ColouredPolygon> mutation = new AddVertexMutation(canvasSize,
+                                                                               Probability.ZERO);
+
+        List<ColouredPolygon> evolved = mutation.apply(image, ExamplesTestUtils.getRNG());
+        assert evolved.size() == 1 : "Polygon count should not be altered by mutation.";
+        ColouredPolygon evolvedPolygon = evolved.get(0);
+        List<Point> vertices = evolvedPolygon.getVertices();
+        assert vertices.size() == polygon.getVertices().size() : "Polygon should have no extra points after mutation.";
+        assert evolvedPolygon == polygon : "Polygon should not have been changed at all.";
+    }
+
+
+    /**
+     * If the image already has the maximum permitted number of points, extra points
+     * should not be added by mutation.
+     */
+    @Test
+    public void testAddMaxPoints()
+    {
+        List<Point> points = new ArrayList<Point>(AddVertexMutation.MAX_VERTEX_COUNT);
+        for (int i = 0; i < AddVertexMutation.MAX_VERTEX_COUNT; i++)
+        {
+            points.add(new Point(i, i));
+        }
+        ColouredPolygon polygon = new ColouredPolygon(Color.RED, points);
+        List<ColouredPolygon> image = new ArrayList<ColouredPolygon>(1);
+        image.add(polygon);
+
+        EvolutionaryOperator<ColouredPolygon> mutation = new AddVertexMutation(canvasSize,
+                                                                               Probability.ONE);
+
+        List<ColouredPolygon> evolved = mutation.apply(image, ExamplesTestUtils.getRNG());
+        assert evolved.size() == 1 : "Polygon count should not be altered by mutation.";
+        ColouredPolygon evolvedPolygon = evolved.get(0);
+        List<Point> vertices = evolvedPolygon.getVertices();
+        assert vertices.size() == polygon.getVertices().size() : "Polygon should have no extra points after mutation.";
+        assert evolvedPolygon == polygon : "Polygon should not have been changed at all.";
+    }
+}
diff --git a/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/monalisa/AdjustVertexMutationTest.java b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/monalisa/AdjustVertexMutationTest.java
new file mode 100644
index 0000000..a4b8142
--- /dev/null
+++ b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/monalisa/AdjustVertexMutationTest.java
@@ -0,0 +1,115 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.monalisa;
+
+import java.awt.Color;
+import java.awt.Dimension;
+import java.awt.Point;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import org.testng.annotations.Test;
+import org.uncommons.maths.number.ConstantGenerator;
+import org.uncommons.maths.random.Probability;
+import org.uncommons.watchmaker.examples.ExamplesTestUtils;
+import org.uncommons.watchmaker.framework.EvolutionaryOperator;
+
+/**
+ * Unit test for the {@link AdjustVertexMutation} evolutionary operator.
+ * @author Daniel Dyer
+ */
+public class AdjustVertexMutationTest
+{
+    private final Dimension canvasSize = new Dimension(200, 200);
+
+    @Test
+    public void testAdjustVertex()
+    {
+        final Point point1 = new Point(1, 1);
+        final Point point2 = new Point(2, 2);
+        final Point point3 = new Point(3, 3);
+        List<Point> points = Arrays.asList(point1, point2, point3);
+        ColouredPolygon polygon = new ColouredPolygon(Color.RED, points);
+        List<ColouredPolygon> image = new ArrayList<ColouredPolygon>(1);
+        image.add(polygon);
+
+        final int amount = 5;        
+        EvolutionaryOperator<ColouredPolygon> mutation = new AdjustVertexMutation(canvasSize,
+                                                                                  Probability.ONE,
+                                                                                  new ConstantGenerator<Integer>(amount));
+
+        List<ColouredPolygon> evolved = mutation.apply(image, ExamplesTestUtils.getRNG());
+        assert evolved.size() == 1 : "Polygon count should not be altered by mutation.";
+        ColouredPolygon evolvedPolygon = evolved.get(0);
+        List<Point> vertices = evolvedPolygon.getVertices();
+        assert vertices.size() == polygon.getVertices().size() : "Polygon should have same number of points after mutation.";
+
+        if (vertices.get(0) != point1)
+        {
+            Point newPoint = vertices.get(0);
+            assert newPoint.x == point1.x + 5 : "X-coordinate not mutated properly.";
+            assert newPoint.y == point1.y + 5 : "Y-coordinate not mutated properly.";
+            // If the first point is different the other two should be the same.
+            assert vertices.get(1) == point2 : "Second point should be unchanged.";
+            assert vertices.get(2) == point3 : "Third point should be unchanged.";
+        }
+        else if (vertices.get(1) != point2)
+        {
+            Point newPoint = vertices.get(1);
+            assert newPoint.x == point2.x + 5 : "X-coordinate not mutated properly.";
+            assert newPoint.y == point2.y + 5 : "Y-coordinate not mutated properly.";
+            // If the second point is different the other two should be the same.
+            assert vertices.get(0) == point1 : "First point should be unchanged.";
+            assert vertices.get(2) == point3 : "Third point should be unchanged.";
+        }
+        else if (vertices.get(2) != point3)
+        {
+            Point newPoint = vertices.get(2);
+            assert newPoint.x == point3.x + 5 : "X-coordinate not mutated properly.";
+            assert newPoint.y == point3.y + 5 : "Y-coordinate not mutated properly.";
+            // If the third point is different the other two should be the same.
+            assert vertices.get(0) == point1 : "Third point should be unchanged.";
+            assert vertices.get(1) == point2 : "Second point should be unchanged.";
+        }
+    }
+
+
+    @Test
+    public void testZeroProbability()
+    {
+        Point point1 = new Point(1, 1);
+        Point point2 = new Point(2, 2);
+        Point point3 = new Point(3, 3);
+        List<Point> points = Arrays.asList(point1, point2, point3);
+        ColouredPolygon polygon = new ColouredPolygon(Color.RED, points);
+        List<ColouredPolygon> image = new ArrayList<ColouredPolygon>(1);
+        image.add(polygon);
+
+        EvolutionaryOperator<ColouredPolygon> mutation = new AdjustVertexMutation(canvasSize,
+                                                                                  Probability.ZERO,
+                                                                                  new ConstantGenerator<Integer>(1));
+
+        List<ColouredPolygon> evolved = mutation.apply(image, ExamplesTestUtils.getRNG());
+        assert evolved.size() == 1 : "Polygon count should not be altered by mutation.";
+        ColouredPolygon evolvedPolygon = evolved.get(0);
+        List<Point> vertices = evolvedPolygon.getVertices();
+        assert vertices.size() == polygon.getVertices().size() : "Polygon should have same number of points after mutation.";
+        assert evolvedPolygon == polygon : "Polygon should not have been changed at all.";
+        assert vertices.get(0) == point1 : "First point should be unchanged.";
+        assert vertices.get(1) == point2 : "Second point should be unchanged.";
+        assert vertices.get(2) == point3 : "Third point should be unchanged.";
+    }
+}
diff --git a/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/monalisa/MovePolygonMutationTest.java b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/monalisa/MovePolygonMutationTest.java
new file mode 100644
index 0000000..cf679e8
--- /dev/null
+++ b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/monalisa/MovePolygonMutationTest.java
@@ -0,0 +1,75 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.monalisa;
+
+import java.awt.Dimension;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import org.testng.annotations.Test;
+import org.uncommons.maths.random.Probability;
+import org.uncommons.watchmaker.examples.ExamplesTestUtils;
+import org.uncommons.watchmaker.framework.EvolutionaryOperator;
+
+/**
+ * Unit test for the {@link MovePolygonMutation} evolutionary operator.
+ * @author Daniel Dyer
+ */
+public class MovePolygonMutationTest
+{
+    private final PolygonImageFactory factory = new PolygonImageFactory(new Dimension(200, 200));
+
+    @Test
+    public void testMovePolygon()
+    {
+        List<ColouredPolygon> image = Arrays.asList(factory.createRandomPolygon(ExamplesTestUtils.getRNG()),
+                                                    factory.createRandomPolygon(ExamplesTestUtils.getRNG()),
+                                                    factory.createRandomPolygon(ExamplesTestUtils.getRNG()),
+                                                    factory.createRandomPolygon(ExamplesTestUtils.getRNG()));
+        List<List<ColouredPolygon>> list = new ArrayList<List<ColouredPolygon>>(1);
+        list.add(image);
+
+        EvolutionaryOperator<List<ColouredPolygon>> mutation = new MovePolygonMutation(Probability.ONE);
+
+        List<List<ColouredPolygon>> evolved = mutation.apply(list, ExamplesTestUtils.getRNG());
+        assert evolved.size() == 1 : "Population size should not be altered by mutation.";
+        assert evolved.get(0).size() == image.size() : "Image should have same number of polygons after mutation.";
+        // Can't reliably test that the order was mutated because the random selection may have moved
+        // the polygon back to its original index.
+    }
+
+
+    @Test
+    public void testZeroProbability()
+    {
+        ColouredPolygon polygon1 = factory.createRandomPolygon(ExamplesTestUtils.getRNG());
+        ColouredPolygon polygon2 = factory.createRandomPolygon(ExamplesTestUtils.getRNG());
+        ColouredPolygon polygon3 = factory.createRandomPolygon(ExamplesTestUtils.getRNG());
+        List<ColouredPolygon> image = Arrays.asList(polygon1, polygon2, polygon3);
+        List<List<ColouredPolygon>> list = new ArrayList<List<ColouredPolygon>>(1);
+        list.add(image);
+
+        EvolutionaryOperator<List<ColouredPolygon>> mutation = new MovePolygonMutation(Probability.ZERO);
+
+        List<List<ColouredPolygon>> evolved = mutation.apply(list, ExamplesTestUtils.getRNG());
+        assert evolved.size() == 1 : "Population size should not be altered by mutation.";
+        assert evolved.get(0).size() == image.size() : "Image should have same number of polygons.";
+        assert evolved.get(0) == image : "Image should not have been changed at all.";
+        assert evolved.get(0).get(0) == polygon1 : "First polygon should not have moved.";
+        assert evolved.get(0).get(1) == polygon2 : "Second polygon should not have moved.";
+        assert evolved.get(0).get(2) == polygon3 : "Third polygon should not have moved.";
+    }
+}
diff --git a/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/monalisa/PolygonColourMutationTest.java b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/monalisa/PolygonColourMutationTest.java
new file mode 100644
index 0000000..bbdb1f9
--- /dev/null
+++ b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/monalisa/PolygonColourMutationTest.java
@@ -0,0 +1,69 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.monalisa;
+
+import java.awt.Color;
+import java.awt.Point;
+import java.util.Arrays;
+import java.util.List;
+import org.testng.annotations.Test;
+import org.uncommons.maths.number.ConstantGenerator;
+import org.uncommons.maths.random.Probability;
+import org.uncommons.watchmaker.examples.ExamplesTestUtils;
+
+/**
+ * Unit test for the {@link PolygonColourMutation} evolutionary operator.
+ * @author Daniel Dyer
+ */
+public class PolygonColourMutationTest
+{
+    @Test
+    public void testColourMutation()
+    {
+        PolygonColourMutation mutation = new PolygonColourMutation(Probability.ONE, // Guaranteed mutation.
+                                                                   new ConstantGenerator<Double>(1d));
+        // A grey triangle.
+        final ColouredPolygon polygon = new ColouredPolygon(new Color(128, 128, 128, 128),
+                                                            Arrays.asList(new Point(0, 0),
+                                                                          new Point(50, 50),
+                                                                          new Point(0, 75)));
+        List<ColouredPolygon> image = Arrays.asList(polygon);
+        List<ColouredPolygon> mutatedImage = mutation.apply(image, ExamplesTestUtils.getRNG());
+        Color mutatedColour = mutatedImage.get(0).getColour();
+        assert mutatedColour.getRed() == 129 : "Red component should have been incremented, is " + mutatedColour.getRed();
+        assert mutatedColour.getGreen() == 129 : "Green component should have been incremented, is " + mutatedColour.getGreen();
+        assert mutatedColour.getBlue() == 129 : "Blue component should have been incremented, is " + mutatedColour.getBlue();
+        assert mutatedColour.getAlpha() == 129 : "Alpha component should have been incremented, is " + mutatedColour.getAlpha();
+    }
+
+
+    @Test
+    public void testZeroProbability()
+    {
+        PolygonColourMutation mutation = new PolygonColourMutation(Probability.ZERO,
+                                                                   new ConstantGenerator<Double>(1d));
+        // A grey triangle.
+        Color originalColour = new Color(128, 128, 128, 128);
+        final ColouredPolygon polygon = new ColouredPolygon(originalColour,
+                                                            Arrays.asList(new Point(0, 0),
+                                                                          new Point(50, 50),
+                                                                          new Point(0, 75)));
+        List<ColouredPolygon> image = Arrays.asList(polygon);
+        List<ColouredPolygon> mutatedImage = mutation.apply(image, ExamplesTestUtils.getRNG());
+        assert mutatedImage.get(0) == polygon : "Polygon should not have changed at all.";
+        assert mutatedImage.get(0).getColour() == originalColour : "Colour should not have changed at all.";
+    }
+}
diff --git a/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/monalisa/PolygonImageEvaluatorTest.java b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/monalisa/PolygonImageEvaluatorTest.java
new file mode 100644
index 0000000..fbd94e8
--- /dev/null
+++ b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/monalisa/PolygonImageEvaluatorTest.java
@@ -0,0 +1,101 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.monalisa;
+
+import java.awt.Color;
+import java.awt.Dimension;
+import java.awt.Point;
+import java.awt.image.BufferedImage;
+import java.util.Arrays;
+import java.util.List;
+import org.testng.annotations.Test;
+import org.uncommons.maths.random.MersenneTwisterRNG;
+
+/**
+ * Unit test for {@link PolygonImageEvaluator}.
+ * @author Daniel Dyer
+ */
+public class PolygonImageEvaluatorTest
+{
+    /**
+     * An image that is identical to the target image should have a fitness
+     * of zero. 
+     */
+    @Test(groups = "display-required")
+    public void testPerfectMatch()
+    {
+        Dimension canvasSize = new Dimension(100, 100);
+        PolygonImageFactory factory = new PolygonImageFactory(canvasSize);
+        List<ColouredPolygon> image = factory.generateRandomCandidate(new MersenneTwisterRNG());
+
+        BufferedImage targetImage = new PolygonImageRenderer(canvasSize, false, null).render(image);
+        PolygonImageEvaluator evaluator = new PolygonImageEvaluator(targetImage);
+
+        double fitness = evaluator.getFitness(image, null);
+        assert fitness == 0 : "Fitness should be zero when image is an exact match.";
+    }
+
+
+    /**
+     * An image that is different to the target image should have a non-zero fitness.
+     */
+    @Test(groups = "display-required")
+    public void testDifferentImages()
+    {
+        Dimension canvasSize = new Dimension(100, 100);
+        List<ColouredPolygon> targetImage = Arrays.asList(new ColouredPolygon(Color.BLACK,
+                                                                              Arrays.asList(new Point(0, 0),
+                                                                                            new Point(99, 0),
+                                                                                            new Point(99, 99),
+                                                                                            new Point(0, 99))));
+        List<ColouredPolygon> candidateImage = Arrays.asList(new ColouredPolygon(Color.WHITE,
+                                                                                 Arrays.asList(new Point(0, 0),
+                                                                                               new Point(99, 0),
+                                                                                               new Point(99, 99),
+                                                                                               new Point(0, 99))));
+
+        BufferedImage renderedTarget = new PolygonImageRenderer(canvasSize, false, null).render(targetImage);
+        PolygonImageEvaluator evaluator = new PolygonImageEvaluator(renderedTarget);
+
+        double fitness = evaluator.getFitness(candidateImage, null);
+        assert fitness > 0 : "Fitness should be non-zero when image does not match target.";
+    }
+
+
+    /**
+     * If the image is not INT_RGB, it will be converted.  This should not affect the results.
+     */
+    @Test(groups = "display-required")
+    public void testImageConversion()
+    {
+        Dimension canvasSize = new Dimension(100, 100);
+        PolygonImageFactory factory = new PolygonImageFactory(canvasSize);
+        List<ColouredPolygon> image = factory.generateRandomCandidate(new MersenneTwisterRNG());
+
+        BufferedImage targetImage = new PolygonImageRenderer(canvasSize, false, null).render(image);
+        // Convert target image to some format that will have to be converted to INT_RGB.
+        BufferedImage newImage = new BufferedImage(targetImage.getWidth(),
+                                                   targetImage.getHeight(),
+                                                   BufferedImage.TYPE_3BYTE_BGR); // Sub-optimal image type.
+        newImage.getGraphics().drawImage(targetImage, 0, 0, null);
+
+        PolygonImageEvaluator evaluator = new PolygonImageEvaluator(newImage);
+
+        double fitness = evaluator.getFitness(image, null);
+        assert fitness == 0 : "Fitness should be zero when image is an exact match.";
+    }
+
+}
diff --git a/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/monalisa/PolygonImageFactoryTest.java b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/monalisa/PolygonImageFactoryTest.java
new file mode 100644
index 0000000..15b2db4
--- /dev/null
+++ b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/monalisa/PolygonImageFactoryTest.java
@@ -0,0 +1,59 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.monalisa;
+
+import java.awt.Dimension;
+import java.awt.Point;
+import java.util.List;
+import org.testng.annotations.Test;
+import org.uncommons.watchmaker.examples.ExamplesTestUtils;
+import org.uncommons.watchmaker.framework.CandidateFactory;
+
+/**
+ * Unit test for {@link PolygonImageFactory}.
+ * @author Daniel Dyer
+ */
+public class PolygonImageFactoryTest
+{
+    /**
+     * Make sure that the generated images have the correct number of polygons,
+     * that each polygon has the correct number of points and that all of the
+     * points fall within the bounds of the specified canvas.
+     */
+    @Test
+    public void testConstraints()
+    {
+        final int width = 100;
+        final int height = 50;
+        CandidateFactory<List<ColouredPolygon>> factory = new PolygonImageFactory(new Dimension(width, height));
+        List<List<ColouredPolygon>> candidates = factory.generateInitialPopulation(20, ExamplesTestUtils.getRNG());
+        for (List<ColouredPolygon> image : candidates)
+        {
+            assert image.size() == PolygonImageFactory.MINIMUM_POLYGON_COUNT
+                : "Wrong number of polygons: " + image.size();
+            for (ColouredPolygon polygon : image)
+            {
+                assert polygon.getVertices().size() == PolygonImageFactory.MINIMUM_VERTEX_COUNT
+                    : "Wrong number of vertices: " + polygon.getVertices().size();
+                for (Point point : polygon.getVertices())
+                {
+                    assert point.x >= 0 && point.x < width : "X out-of-range: " + point.x;
+                    assert point.y >= 0 && point.y < height : "Y out-of-range: " + point.y;
+                }
+            }
+        }
+    }
+}
diff --git a/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/monalisa/ProbabilitiesPanelTest.java b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/monalisa/ProbabilitiesPanelTest.java
new file mode 100644
index 0000000..3e44663
--- /dev/null
+++ b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/monalisa/ProbabilitiesPanelTest.java
@@ -0,0 +1,132 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.monalisa;
+
+import java.awt.BorderLayout;
+import java.awt.Color;
+import java.awt.Dimension;
+import java.awt.Point;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import javax.swing.JFrame;
+import org.fest.swing.core.BasicRobot;
+import org.fest.swing.core.Robot;
+import org.fest.swing.fixture.FrameFixture;
+import org.testng.annotations.AfterMethod;
+import org.testng.annotations.BeforeMethod;
+import org.testng.annotations.Test;
+import org.uncommons.watchmaker.examples.ExamplesTestUtils;
+import org.uncommons.watchmaker.framework.EvolutionaryOperator;
+
+/**
+ * Unit test for the {@link ProbabilitiesPanel} class.
+ * @author Daniel Dyer
+ */
+public class ProbabilitiesPanelTest
+{
+    private Robot robot;
+
+    @BeforeMethod(groups = "display-required")
+    public void prepare()
+    {
+        robot = BasicRobot.robotWithNewAwtHierarchy();
+    }
+
+
+    @AfterMethod(groups = "display-required")
+    public void cleanUp()
+    {
+        robot.cleanUp();
+        robot = null;
+    }
+    
+    @Test(groups = "display-required")
+    public void testSetAllProbabilitiesToZero()
+    {
+        ProbabilitiesPanel panel = new ProbabilitiesPanel();
+        JFrame frame = new JFrame();
+        frame.add(panel, BorderLayout.CENTER);
+        FrameFixture frameFixture = new FrameFixture(robot, frame);
+        frame.setSize(700, 300);
+        frame.validate();
+
+        frameFixture.show();
+        frameFixture.panel("AddPolygon").slider().slideToMinimum();
+        frameFixture.panel("RemovePolygon").slider().slideToMinimum();
+        frameFixture.panel("MovePolygon").slider().slideToMinimum();
+        frameFixture.panel("Cross-over").slider().slideToMinimum();
+        frameFixture.panel("AddVertex").slider().slideToMinimum();
+        frameFixture.panel("RemoveVertex").slider().slideToMinimum();
+        frameFixture.panel("MoveVertex").slider().slideToMinimum();
+        frameFixture.panel("ChangeColour").slider().slideToMinimum();
+
+        Dimension canvasSize = new Dimension(100, 100);
+        PolygonImageFactory factory = new PolygonImageFactory(canvasSize);
+        EvolutionaryOperator<List<ColouredPolygon>> operator = panel.createEvolutionPipeline(factory,
+                                                                                             canvasSize,
+                                                                                             ExamplesTestUtils.getRNG());
+        List<ColouredPolygon> candidate1 = Arrays.asList(new ColouredPolygon(Color.WHITE,
+                                                                             Arrays.asList(new Point(1, 1))));
+        List<ColouredPolygon> candidate2 = Arrays.asList(new ColouredPolygon(Color.BLACK,
+                                                                             Arrays.asList(new Point(2, 2))));
+        List<List<ColouredPolygon>> population = new ArrayList<List<ColouredPolygon>>(2);
+        population.add(candidate1);
+        population.add(candidate2);
+        
+        List<List<ColouredPolygon>> evolved = operator.apply(population,
+                                                             ExamplesTestUtils.getRNG());
+        // Candidate order may have changed, but individual candidates should remain unaltered.
+        assert (checkEquals(evolved.get(0), candidate1) && checkEquals(evolved.get(1), candidate2))
+               || (checkEquals(evolved.get(0), candidate2) && checkEquals(evolved.get(1), candidate1))
+            : "Candidates should be unaltered when all probabilities are zero.";
+    }
+
+
+    private boolean checkEquals(List<ColouredPolygon> candidate1,
+                                List<ColouredPolygon> candidate2)
+    {
+        if (candidate1.size() != candidate2.size())
+        {
+            return false;
+        }
+        for (int i = 0; i < candidate1.size(); i++)
+        {
+            ColouredPolygon polygon1 = candidate1.get(i);
+            ColouredPolygon polygon2 = candidate2.get(i);
+            if (!polygon1.getColour().equals(polygon2.getColour()))
+            {
+                return false;
+            }
+            List<Point> vertices1 = polygon1.getVertices();
+            List<Point> vertices2 = polygon2.getVertices();
+            if (vertices1.size() != vertices2.size())
+            {
+                return false;
+            }
+            for (int j = 0; j < vertices1.size(); j++)
+            {
+                Point point1 = vertices1.get(j);
+                Point point2 = vertices2.get(j);
+                if (point1.x != point2.x || point1.y != point2.y)
+                {
+                    return false;
+                }
+            }
+        }
+        return true;
+    }
+}
diff --git a/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/monalisa/RemovePolygonMutationTest.java b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/monalisa/RemovePolygonMutationTest.java
new file mode 100644
index 0000000..bcd5f6c
--- /dev/null
+++ b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/monalisa/RemovePolygonMutationTest.java
@@ -0,0 +1,91 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.monalisa;
+
+import java.awt.Dimension;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import org.testng.annotations.Test;
+import org.uncommons.maths.random.Probability;
+import org.uncommons.watchmaker.examples.ExamplesTestUtils;
+import org.uncommons.watchmaker.framework.EvolutionaryOperator;
+
+/**
+ * Unit test for the {@link RemovePolygonMutation} evolutionary operator.
+ * @author Daniel Dyer
+ */
+public class RemovePolygonMutationTest
+{
+    private final PolygonImageFactory factory = new PolygonImageFactory(new Dimension(200, 200));
+
+    @Test
+    public void testRemovePolygon()
+    {
+        List<ColouredPolygon> image = Arrays.asList(factory.createRandomPolygon(ExamplesTestUtils.getRNG()),
+                                                    factory.createRandomPolygon(ExamplesTestUtils.getRNG()),
+                                                    factory.createRandomPolygon(ExamplesTestUtils.getRNG()),
+                                                    factory.createRandomPolygon(ExamplesTestUtils.getRNG()));
+        List<List<ColouredPolygon>> list = new ArrayList<List<ColouredPolygon>>(1);
+        list.add(image);
+
+        EvolutionaryOperator<List<ColouredPolygon>> mutation = new RemovePolygonMutation(Probability.ONE);
+
+        List<List<ColouredPolygon>> evolved = mutation.apply(list, ExamplesTestUtils.getRNG());
+        assert evolved.size() == 1 : "Population size should not be altered by mutation.";
+        assert evolved.get(0).size() == image.size() - 1 : "Image should have 1 fewer polygon after mutation.";
+    }
+
+
+    @Test
+    public void testZeroProbability()
+    {
+        List<ColouredPolygon> image = Arrays.asList(factory.createRandomPolygon(ExamplesTestUtils.getRNG()),
+                                                    factory.createRandomPolygon(ExamplesTestUtils.getRNG()),
+                                                    factory.createRandomPolygon(ExamplesTestUtils.getRNG()),
+                                                    factory.createRandomPolygon(ExamplesTestUtils.getRNG()));
+        List<List<ColouredPolygon>> list = new ArrayList<List<ColouredPolygon>>(1);
+        list.add(image);
+
+        EvolutionaryOperator<List<ColouredPolygon>> mutation = new RemovePolygonMutation(Probability.ZERO);
+
+        List<List<ColouredPolygon>> evolved = mutation.apply(list, ExamplesTestUtils.getRNG());
+        assert evolved.size() == 1 : "Population size should not be altered by mutation.";
+        assert evolved.get(0).size() == image.size() : "Image should have same number of polygons.";
+        assert evolved.get(0) == image : "Image should not have been changed at all.";
+    }
+
+
+    /**
+     * If the image already has the minimum permitted number of polygons, further polygons
+     * should not be removed by mutation.
+     */
+    @Test
+    public void testRemoveMinPolygons()
+    {
+        List<ColouredPolygon> image = factory.generateRandomCandidate(ExamplesTestUtils.getRNG());
+        assert image.size() == 2 : "Image should have 2 polygons";
+        List<List<ColouredPolygon>> list = new ArrayList<List<ColouredPolygon>>(1);
+        list.add(image);
+
+        EvolutionaryOperator<List<ColouredPolygon>> mutation = new RemovePolygonMutation(Probability.ONE);
+
+        List<List<ColouredPolygon>> evolved = mutation.apply(list, ExamplesTestUtils.getRNG());
+        assert evolved.size() == 1 : "Population size should not be altered by mutation.";
+        assert evolved.get(0).size() == image.size() : "Image should have no fewer than the minimum number of polygons.";
+        assert evolved.get(0) == image : "Image should not have been changed at all.";
+    }
+}
diff --git a/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/monalisa/RemoveVertexMutationTest.java b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/monalisa/RemoveVertexMutationTest.java
new file mode 100644
index 0000000..e204d55
--- /dev/null
+++ b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/monalisa/RemoveVertexMutationTest.java
@@ -0,0 +1,98 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.monalisa;
+
+import java.awt.Color;
+import java.awt.Dimension;
+import java.awt.Point;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import org.testng.annotations.Test;
+import org.uncommons.maths.random.Probability;
+import org.uncommons.watchmaker.examples.ExamplesTestUtils;
+import org.uncommons.watchmaker.framework.EvolutionaryOperator;
+
+/**
+ * Unit test for the {@link RemoveVertexMutation} evolutionary operator.
+ * @author Daniel Dyer
+ */
+public class RemoveVertexMutationTest
+{
+    private final Dimension canvasSize = new Dimension(200, 200);
+
+    @Test
+    public void testRemoveVertex()
+    {
+        List<Point> points = Arrays.asList(new Point(1, 1), new Point(2, 2), new Point(3, 3), new Point(4, 4));
+        ColouredPolygon polygon = new ColouredPolygon(Color.RED, points);
+        List<ColouredPolygon> image = new ArrayList<ColouredPolygon>(1);
+        image.add(polygon);
+
+        EvolutionaryOperator<ColouredPolygon> mutation = new RemoveVertexMutation(canvasSize,
+                                                                                  Probability.ONE);
+
+        List<ColouredPolygon> evolved = mutation.apply(image, ExamplesTestUtils.getRNG());
+        assert evolved.size() == 1 : "Polygon count should not be altered by mutation.";
+        List<Point> vertices = evolved.get(0).getVertices();
+        assert vertices.size() == polygon.getVertices().size() - 1
+            : "Polygon should have 1 fewer point after mutation.";
+    }
+
+
+    @Test
+    public void testZeroProbability()
+    {
+        List<Point> points = Arrays.asList(new Point(1, 1), new Point(2, 2), new Point(3, 3), new Point(4, 4));
+        ColouredPolygon polygon = new ColouredPolygon(Color.RED, points);
+        List<ColouredPolygon> image = new ArrayList<ColouredPolygon>(1);
+        image.add(polygon);
+
+        EvolutionaryOperator<ColouredPolygon> mutation = new RemoveVertexMutation(canvasSize,
+                                                                                  Probability.ZERO);
+
+        List<ColouredPolygon> evolved = mutation.apply(image, ExamplesTestUtils.getRNG());
+        assert evolved.size() == 1 : "Polygon count should not be altered by mutation.";
+        ColouredPolygon evolvedPolygon = evolved.get(0);
+        List<Point> vertices = evolvedPolygon.getVertices();
+        assert vertices.size() == polygon.getVertices().size() : "Polygon should have no fewer points after mutation.";
+        assert evolvedPolygon == polygon : "Polygon should not have been changed at all.";
+    }
+
+
+    /**
+     * If the image already has the minimum permitted number of points, further points
+     * should not be removed by mutation.
+     */
+    @Test
+    public void testAddMaxPoints()
+    {
+        List<Point> points = Arrays.asList(new Point(1, 1), new Point(2, 2), new Point(3, 3));
+        ColouredPolygon polygon = new ColouredPolygon(Color.RED, points);
+        List<ColouredPolygon> image = new ArrayList<ColouredPolygon>(1);
+        image.add(polygon);
+
+        EvolutionaryOperator<ColouredPolygon> mutation = new RemoveVertexMutation(canvasSize,
+                                                                                  Probability.ONE);
+
+        List<ColouredPolygon> evolved = mutation.apply(image, ExamplesTestUtils.getRNG());
+        assert evolved.size() == 1 : "Polygon count should not be altered by mutation.";
+        ColouredPolygon evolvedPolygon = evolved.get(0);
+        List<Point> vertices = evolvedPolygon.getVertices();
+        assert vertices.size() == polygon.getVertices().size() : "Polygon should have no fewer points after mutation.";
+        assert evolvedPolygon == polygon : "Polygon should not have been changed at all.";
+    }
+}
diff --git a/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/strings/StringEvaluatorTest.java b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/strings/StringEvaluatorTest.java
new file mode 100644
index 0000000..54a3dd4
--- /dev/null
+++ b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/strings/StringEvaluatorTest.java
@@ -0,0 +1,58 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.strings;
+
+import org.testng.annotations.Test;
+import org.uncommons.watchmaker.framework.FitnessEvaluator;
+
+/**
+ * Unit test for fitness function used by the strings example.
+ * @author Daniel Dyer
+ */
+public class StringEvaluatorTest
+{
+    @Test
+    public void testIdentical()
+    {
+        String target = "abcdefgh";
+        String candidate = "abcdefgh";
+        FitnessEvaluator<String> evaluator = new StringEvaluator(target);
+        int score = (int) evaluator.getFitness(candidate, null);
+        assert score == 0 : "Fitness should be zero for identical strings, is " + score;
+    }
+
+
+    @Test
+    public void testCompletelyDifferent()
+    {
+        String target = "abcdefgh";
+        String candidate = "ijklmnop";
+        FitnessEvaluator<String> evaluator = new StringEvaluator(target);
+        int score = (int) evaluator.getFitness(candidate, null);
+        assert score == target.length() : "Fitness should be " + target.length() + ", is " + score;
+    }
+
+
+    @Test
+    public void testPartialSolution()
+    {
+        String target = "abcdefgh";
+        String candidate = "abcdxxxx";
+        FitnessEvaluator<String> evaluator = new StringEvaluator(target);
+        int score = (int) evaluator.getFitness(candidate, null);
+        assert score == 4 : "Fitness score should be 4, is " + score;
+    }
+}
diff --git a/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/strings/StringsExampleTest.java b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/strings/StringsExampleTest.java
new file mode 100644
index 0000000..ab54121
--- /dev/null
+++ b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/strings/StringsExampleTest.java
@@ -0,0 +1,34 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.strings;
+
+import org.testng.annotations.Test;
+
+/**
+ * Simple unit test for the Strings example.  Makes sure that the evolution engine
+ * eventually returns the target String.
+ * @author Daniel Dyer
+ */
+public class StringsExampleTest
+{
+    @Test
+    public void testEvolution()
+    {
+        String target = "WATCHMAKER";
+        String result = StringsExample.evolveString(target);
+        assert result.equals(target) : "Evolution returned wrong result: " + result;
+    }
+}
diff --git a/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/sudoku/SudokuCellRendererTest.java b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/sudoku/SudokuCellRendererTest.java
new file mode 100644
index 0000000..e1f3df3
--- /dev/null
+++ b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/sudoku/SudokuCellRendererTest.java
@@ -0,0 +1,112 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.sudoku;
+
+import java.awt.Color;
+import javax.swing.JLabel;
+import javax.swing.JTable;
+import javax.swing.table.TableCellRenderer;
+import org.testng.annotations.BeforeClass;
+import org.testng.annotations.Test;
+
+/**
+ * Unit test for the {@link SudokuCellRenderer} class.
+ * @author Daniel Dyer
+ */
+public class SudokuCellRendererTest
+{
+    private JTable table;
+
+
+    @Test
+    public void testRenderFixedCells()
+    {
+        SudokuTableModel model = new SudokuTableModel();
+        // Set the 2 lefthand cells in the top row.
+        model.setValueAt('1', 0, 0);
+        model.setValueAt('2', 0, 1);
+
+        JTable table = new JTable(model);
+        TableCellRenderer renderer = new SudokuCellRenderer();
+
+        JLabel cell1 = (JLabel) renderer.getTableCellRendererComponent(table, '1', false, false, 0, 0);
+        assert cell1.getText().equals("1") : "Wrong text at cell 1: " + cell1.getText();
+        assert cell1.getFont().isBold() : "Fixed cells should be rendered in bold.";
+        JLabel cell2 = (JLabel) renderer.getTableCellRendererComponent(table, '2', false, false, 0, 1);
+        assert cell2.getText().equals("2") : "Wrong text at cell 2: " + cell2.getText();
+        assert cell2.getFont().isBold() : "Fixed cells should be rendered in bold.";
+        // Check an empty cell, it should have no text.
+        JLabel cell3 = (JLabel) renderer.getTableCellRendererComponent(table, null, false, false, 0, 2);
+        assert cell3.getText().length() == 0 : "Wrong text at cell 3: " + cell3.getText();
+    }
+
+
+    @BeforeClass
+    public void createTable()
+    {
+        SudokuTableModel model = new SudokuTableModel();
+        model.setSudoku(SudokuTestUtils.createSudoku(new int[][]{{3, 2, 4, 8, 9, 1, 7, 5, 6},
+                                                                 {6, 9, 7, 1, 5, 2, 8, 4, 3},
+                                                                 {8, 1, 5, 7, 3, 6, 4, 2, 9},
+                                                                 {5, 2, 6, 9, 7, 4, 3, 1, 8},
+                                                                 {4, 9, 8, 1, 2, 5, 6, 7, 3},
+                                                                 {8, 7, 1, 3, 4, 2, 9, 6, 5},
+                                                                 {2, 6, 3, 4, 8, 7, 5, 9, 1},
+                                                                 {1, 3, 5, 8, 4, 9, 2, 6, 7},
+                                                                 {7, 4, 2, 1, 5, 3, 9, 8, 6}}));
+        table = new JTable(model);
+    }
+
+
+    @Test
+    public void testRenderCellWithNoConflicts()
+    {
+        TableCellRenderer renderer = new SudokuCellRenderer();
+        JLabel cell = (JLabel) renderer.getTableCellRendererComponent(table, 1, false, false, 2, 1);
+        assert cell.getText().equals("1") : "Wrong value at cell (2, 1): " + cell.getText();
+        assert cell.getBackground() == Color.WHITE : "Cell without conflicts should be white.";
+    }
+
+
+    @Test
+    public void testRenderCellWithOneConflict()
+    {
+        TableCellRenderer renderer = new SudokuCellRenderer();
+        JLabel cell = (JLabel) renderer.getTableCellRendererComponent(table, 3, false, false, 7, 1);
+        assert cell.getText().equals("3") : "Wrong value at cell (7, 1): " + cell.getText();
+        assert cell.getBackground() == Color.YELLOW : "Cell with one conflict should be yellow.";
+    }
+
+
+    @Test
+    public void testRenderCellWithTwoConflicts()
+    {
+        TableCellRenderer renderer = new SudokuCellRenderer();
+        JLabel cell = (JLabel) renderer.getTableCellRendererComponent(table, 6, false, false, 8, 8);
+        assert cell.getText().equals("6") : "Wrong value at cell (8, 8): " + cell.getText();
+        assert cell.getBackground() == Color.ORANGE : "Cell with two conflicts should be orange.";
+    }
+
+
+    @Test
+    public void testRenderCellWithThreeConflicts()
+    {
+        TableCellRenderer renderer = new SudokuCellRenderer();
+        JLabel cell = (JLabel) renderer.getTableCellRendererComponent(table, 1, false, false, 1, 3);
+        assert cell.getText().equals("1") : "Wrong value at cell (1, 3): " + cell.getText();
+        assert cell.getBackground() == Color.RED : "Cell with two conflicts should be red.";
+    }
+}
diff --git a/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/sudoku/SudokuEvaluatorTest.java b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/sudoku/SudokuEvaluatorTest.java
new file mode 100644
index 0000000..38864fd
--- /dev/null
+++ b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/sudoku/SudokuEvaluatorTest.java
@@ -0,0 +1,77 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.sudoku;
+
+import org.testng.annotations.Test;
+import org.uncommons.watchmaker.framework.FitnessEvaluator;
+
+/**
+ * Unit test for sudoku fitness evaluator.
+ * @author Daniel Dyer
+ */
+public class SudokuEvaluatorTest
+{
+    /**
+     * Ensure that the evaluator returns zero for a correct solution.
+     */
+    @Test
+    public void testCorrectSolution()
+    {
+        Sudoku sudoku = SudokuTestUtils.createSudoku(new int[][]
+        {
+            {1, 2, 8, 5, 4, 3, 9, 6, 7},
+            {7, 6, 4, 9, 2, 8, 5, 1, 3},
+            {3, 9, 5, 7, 6, 1, 2, 4, 8},
+            {6, 1, 9, 4, 8, 5, 7, 3, 2},
+            {5, 8, 3, 6, 7, 2, 1, 9, 4},
+            {4, 7, 2, 3, 1, 9, 8, 5, 6},
+            {8, 5, 1, 2, 3, 6, 4, 7, 9},
+            {9, 4, 6, 8, 5, 7, 3, 2, 1},
+            {2, 3, 7, 1, 9, 4, 6, 8, 5}
+        });
+        FitnessEvaluator<Sudoku> evaluator = new SudokuEvaluator();
+        int fitness = (int) evaluator.getFitness(sudoku, null);
+        assert fitness == 0 : "Fitness should be zero for correct solution, is " + fitness; 
+    }
+
+
+    /**
+     * Ensure that the evaluator returns zero for a correct solution.
+     */
+    @Test
+    public void testDuplicates()
+    {
+        // This sudoku as 4 invalid columns (0, 1, 3 and 5) and 2 invalid
+        // sub-grids (bottom-left and bottom-center).
+        Sudoku sudoku = SudokuTestUtils.createSudoku(new int[][]
+        {
+            {2, 1, 8, 5, 4, 3, 9, 6, 7},
+            {7, 6, 4, 9, 2, 8, 5, 1, 3},
+            {3, 9, 5, 7, 6, 1, 2, 4, 8},
+            {6, 1, 9, 4, 8, 5, 7, 3, 2},
+            {5, 8, 3, 6, 7, 2, 1, 9, 4},
+            {4, 7, 2, 3, 1, 9, 8, 5, 6},
+            {8, 5, 2, 1, 3, 6, 4, 7, 9},
+            {9, 4, 6, 8, 5, 7, 3, 2, 1},
+            {2, 3, 7, 1, 9, 4, 6, 8, 5}
+        });
+        FitnessEvaluator<Sudoku> evaluator = new SudokuEvaluator();
+        int fitness = (int) evaluator.getFitness(sudoku, null);
+        assert fitness == 6 : "Fitness should be 6, is " + fitness;
+    }
+
+
+}
diff --git a/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/sudoku/SudokuFactoryTest.java b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/sudoku/SudokuFactoryTest.java
new file mode 100644
index 0000000..f81cfa6
--- /dev/null
+++ b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/sudoku/SudokuFactoryTest.java
@@ -0,0 +1,142 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.sudoku;
+
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+import org.testng.annotations.Test;
+import org.uncommons.watchmaker.examples.ExamplesTestUtils;
+import org.uncommons.watchmaker.framework.CandidateFactory;
+
+/**
+ * Unit test for sudoku candidate solution factory.
+ * @author Daniel Dyer
+ */
+public class SudokuFactoryTest
+{
+    /**
+     * Checks to make sure that the givens are correctly placed and that each row
+     * contains each value exactly once.
+     */
+    @Test
+    public void testValidity()
+    {
+        CandidateFactory<Sudoku> factory = new SudokuFactory(".9.......",
+                                                             ".........",
+                                                             "........5",
+                                                             "....2....",
+                                                             ".........",
+                                                             ".........",
+                                                             ".........",
+                                                             "...1.....",
+                                                             "........9");
+
+        List<Sudoku> population = factory.generateInitialPopulation(20, ExamplesTestUtils.getRNG());
+        for (Sudoku sudoku : population)
+        {
+            // Check givens are correctly placed.
+            assert sudoku.isFixed(2, 8) : "Cell (2, 8) should be fixed.";
+            assert sudoku.getValue(2, 8) == 5 : "Cell (2, 8) should contain 5.";
+            assert sudoku.isFixed(7, 3) : "Cell (7, 3) should be fixed.";
+            assert sudoku.getValue(7, 3) == 1 : "Cell (7, 3) should contain 1.";
+            assert sudoku.isFixed(3, 4) : "Cell (3, 4) should be fixed.";
+            assert sudoku.getValue(3, 4) == 2 : "Cell (3, 4) should contain 2.";
+            assert sudoku.isFixed(0, 1) : "Cell (0, 1) should be fixed.";
+            assert sudoku.getValue(0, 1) == 9 : "Cell (0, 1) should contain 9.";
+            assert sudoku.isFixed(8, 8) : "Cell (8, 8) should be fixed.";
+            assert sudoku.getValue(8, 8) == 9 : "Cell (8, 8) should contain 9.";
+
+            // Check that each row has no duplicates.
+            Set<Integer> set = new HashSet<Integer>();
+            for (int i = 0; i < 9; i++)
+            {
+                Sudoku.Cell[] row = sudoku.getRow(i);
+                for (Sudoku.Cell cell : row)
+                {
+                    set.add(cell.getValue());
+                }
+                if (set.size() < 9)
+                {
+                    System.out.println(sudoku);
+                    assert false : "Row " + i + " contains duplicates.";
+                }
+            }
+        }
+    }
+
+
+    /**
+     * If the pattern used to create a Sudoku factory contains any characters
+     * other than the values 1 - 9 or dots (which represent empty cells), then
+     * an appropriate exception should be thrown.
+     */
+    @Test(expectedExceptions = IllegalArgumentException.class)
+    public void testInvalidPatternChars()
+    {
+        // This pattern is the right size but contains an invalid character.
+        String[] pattern = {"....9....",
+                            "2..3.....",
+                            "........1",
+                            "....a....", // Invalid character on this line.
+                            "....4....",
+                            ".........",
+                            ".........",
+                            ".........",
+                            "........."};
+        new SudokuFactory(pattern);
+    }
+
+
+    /**
+     * If the pattern used to create a Sudoku factory contains the wrong number
+     * of rows then an appropriate exception should be thrown.
+     */
+    @Test(expectedExceptions = IllegalArgumentException.class)
+    public void testWrongNumberOfRows()
+    {
+        // This pattern contains only valid characters and has the right number
+        // of columns but doesn't have enough rows.
+        String[] pattern = {"....9....",
+                            "2..3.....",
+                            "........1",
+                            ".........",
+                            "........."};
+        new SudokuFactory(pattern);
+    }
+
+
+    /**
+     * If the pattern used to create a Sudoku factory contains the wrong number
+     * of columns then an appropriate exception should be thrown.
+     */
+    @Test(expectedExceptions = IllegalArgumentException.class)
+    public void testWrongNumberOfColumns()
+    {
+        // This pattern contains only valid characters and has the right number
+        // of rows but has too many columns in some
+        String[] pattern = {"....9....",
+                            "2..3.....",
+                            "........1",
+                            ".........",
+                            ".........7",
+                            ".........",
+                            ".4.......6",
+                            "..1.3....",
+                            "........8"};
+        new SudokuFactory(pattern);
+    }
+}
diff --git a/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/sudoku/SudokuRowMutationTest.java b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/sudoku/SudokuRowMutationTest.java
new file mode 100644
index 0000000..9386e83
--- /dev/null
+++ b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/sudoku/SudokuRowMutationTest.java
@@ -0,0 +1,127 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.sudoku;
+
+import java.util.Arrays;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+import org.testng.annotations.Test;
+import org.uncommons.watchmaker.examples.ExamplesTestUtils;
+import org.uncommons.watchmaker.framework.EvolutionaryOperator;
+
+/**
+ * Unit test for Sudoku mutation operator.
+ * @author Daniel Dyer
+ */
+public class SudokuRowMutationTest
+{
+    /**
+     * Tests to ensure that rows are still valid after mutation.  Each row
+     * should contain each value 1-9 exactly once.
+     */
+    @Test
+    public void testValidity()
+    {
+        EvolutionaryOperator<Sudoku> mutation = new SudokuRowMutation(8, 1);
+        List<Sudoku> population = Arrays.asList(SudokuTestUtils.createSudoku(new int[][]
+        {
+            {1, 2, 8, 5, 4, 3, 9, 6, 7},
+            {7, 6, 4, 9, 2, 8, 5, 1, 3},
+            {3, 9, 5, 7, 6, 1, 2, 4, 8},
+            {6, 1, 9, 4, 8, 5, 7, 3, 2},
+            {5, 8, 3, 6, 7, 2, 1, 9, 4},
+            {4, 7, 2, 3, 1, 9, 8, 5, 6},
+            {8, 5, 1, 2, 3, 6, 4, 7, 9},
+            {9, 4, 6, 8, 5, 7, 3, 2, 1},
+            {2, 3, 7, 1, 9, 4, 6, 8, 5}
+        }));
+        final Set<Integer> counts = new HashSet<Integer>(Sudoku.SIZE);
+        for (int i = 0; i < 20; i++)
+        {
+            population = mutation.apply(population, ExamplesTestUtils.getRNG());
+            assert population.size() == 1 : "Population size changed after mutation(s).";
+            Sudoku mutatedSudoku = population.get(0);
+            for (int j = 0; j < Sudoku.SIZE; j++)
+            {
+                Sudoku.Cell[] row = mutatedSudoku.getRow(j);
+                assert row.length == Sudoku.SIZE : "Row length is invalid: " + row.length;
+                for (Sudoku.Cell cell : row)
+                {
+                    int value = cell.getValue();
+                    assert value > 0 && value <= Sudoku.SIZE : "Cell value out of range: " + value;
+                    counts.add(value);
+                }
+                assert counts.size() == Sudoku.SIZE : "Row contains duplicates.";
+                counts.clear();
+            }
+        }
+    }
+
+
+    /**
+     * Check that the mutation never modifies the value of fixed cells.
+     */
+    @Test(dependsOnMethods = "testValidity")
+    public void testFixedConstraints()
+    {
+        EvolutionaryOperator<Sudoku> mutation = new SudokuRowMutation(8, 1);
+        Sudoku.Cell[][] cells = new Sudoku.Cell[Sudoku.SIZE][Sudoku.SIZE];
+        // One cell in each row is fixed (cell 1 in row 1, cell 2 in row 2, etc.)
+        for (int row = 0; row < Sudoku.SIZE; row++)
+        {
+            for (int column = 0; column < Sudoku.SIZE; column++)
+            {
+                cells[row][column] = new Sudoku.Cell(column + 1, column == row);
+            }
+        }
+        List<Sudoku> population = Arrays.asList(new Sudoku(cells));
+        for (int i = 0; i < 100; i++) // 100 generations of mutation.
+        {
+            population = mutation.apply(population, ExamplesTestUtils.getRNG());
+            Sudoku sudoku = population.get(0);
+            for (int row = 0; row < Sudoku.SIZE; row++)
+            {
+                for (int column = 0; column < Sudoku.SIZE; column++)
+                {
+                    if (row == column)
+                    {
+                        assert sudoku.isFixed(row, column) : "Fixed cell has become unfixed.";
+                        assert sudoku.getValue(row, column) == (row + 1) : "Fixed cell has changed value.";
+                    }
+                    else
+                    {
+                        assert !sudoku.isFixed(row, column) : "Unfixed cell has become fixed.";
+                    }
+                }
+            }
+        }
+    }
+
+
+    @Test(expectedExceptions = IllegalArgumentException.class)
+    public void testInvalidMutationCount()
+    {
+        new SudokuRowMutation(0, 1); // Should throw an IllegalArgumentException.
+    }
+
+
+    @Test(expectedExceptions = IllegalArgumentException.class)
+    public void testInvalidMutationAmount()
+    {
+        new SudokuRowMutation(1, 0); // Should throw an IllegalArgumentException.
+    }
+}
diff --git a/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/sudoku/SudokuTableModelTest.java b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/sudoku/SudokuTableModelTest.java
new file mode 100644
index 0000000..30bbf18
--- /dev/null
+++ b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/sudoku/SudokuTableModelTest.java
@@ -0,0 +1,113 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.sudoku;
+
+import org.testng.annotations.Test;
+
+/**
+ * Unit test for the table model used by the Sudoku example application.
+ * @author Daniel Dyer
+ */
+public class SudokuTableModelTest
+{
+    private static final String[] TEST_PUZZLE = {"4.5...9.7",
+                                                 ".2..9..6.",
+                                                 "39.6.7.28",
+                                                 "9..3.2..6",
+                                                 "7..9.6..3",
+                                                 "5..4.8..1",
+                                                 "28.1.5.49",
+                                                 ".7..3..8.",
+                                                 "6.4...3.2"};
+
+    /**
+     * Makes sure that the table model class correctly converts to and from the
+     * String patterns used by {@link SudokuFactory}.
+     */
+    @Test
+    public void testPatternConversions()
+    {
+        SudokuTableModel model = new SudokuTableModel();
+        model.setPattern(TEST_PUZZLE);
+        // Change a cell, to ensure we don't get exactly the same pattern back.
+        model.setValueAt('1', 8, 7);
+        String[] newPattern = model.getPattern();
+        // Make sure the pattern is correct.
+        for (int i = 0; i < 8; i++) // Check the first 8 rows, which haven't changed.
+        {
+            assert newPattern[i].equals(TEST_PUZZLE[i]) : "Row " + i + " incorrect: " + newPattern[i];
+        }
+        // Check modified row.
+        assert newPattern[8].equals("6.4...312") : "Row 8 incorrect: " + newPattern[8]; 
+    }
+
+
+    @Test(expectedExceptions = IllegalArgumentException.class)
+    public void testTooManyRowsInPattern()
+    {
+        SudokuTableModel model = new SudokuTableModel();
+        model.setPattern(new String[]{".........",
+                                      ".........",
+                                      ".........",
+                                      ".........",
+                                      ".........",
+                                      ".........",
+                                      ".........",
+                                      ".........",
+                                      ".........",
+                                      "........."}); // 10 rows should trigger an IllegalArgumentException.
+    }
+
+
+    @Test(expectedExceptions = IllegalArgumentException.class)
+    public void testTooManyColumnsInPattern()
+    {
+        SudokuTableModel model = new SudokuTableModel();
+        model.setPattern(new String[]{"..........",
+                                      "..........",
+                                      "..........",
+                                      "..........",
+                                      "..........",
+                                      "..........",
+                                      "..........",
+                                      "..........",
+                                      ".........."}); // 10 columns in each row should trigger an IllegalArgumentException.
+    }
+
+
+    @Test
+    public void testGetValueAt()
+    {
+        SudokuTableModel model = new SudokuTableModel();
+        model.setSudoku(SudokuTestUtils.createSudoku(new int[][]{{1, 2, 3, 4, 5, 6, 7, 8, 9},
+                                                                 {1, 2, 3, 4, 5, 6, 7, 8, 9},
+                                                                 {1, 2, 3, 4, 5, 6, 7, 8, 9},
+                                                                 {1, 2, 3, 4, 5, 6, 7, 8, 9},
+                                                                 {1, 2, 3, 4, 5, 6, 7, 8, 9},
+                                                                 {1, 2, 3, 4, 5, 6, 7, 8, 9},
+                                                                 {1, 2, 3, 4, 5, 6, 7, 8, 9},
+                                                                 {1, 2, 3, 4, 5, 6, 7, 8, 9},
+                                                                 {1, 2, 3, 4, 5, 6, 7, 8, 9}}));
+        for (int row = 0; row < model.getRowCount(); row++)
+        {
+            for (int column = 0; column < model.getColumnCount(); column++)
+            {
+                int actualCell = (Integer) model.getValueAt(row, column);
+                assert actualCell == column + 1: "Wrong value at " + row + ", " + column + ": " + actualCell; 
+            }
+        }
+    }
+}
diff --git a/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/sudoku/SudokuTest.java b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/sudoku/SudokuTest.java
new file mode 100644
index 0000000..798b0fa
--- /dev/null
+++ b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/sudoku/SudokuTest.java
@@ -0,0 +1,97 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.sudoku;
+
+import org.testng.annotations.Test;
+
+/**
+ * Unit test for the {@link Sudoku} data structure.
+ * @author Daniel Dyer
+ */
+public class SudokuTest
+{
+    @Test(expectedExceptions = IllegalArgumentException.class)
+    public void testWrongNumberOfRows()
+    {
+        // This grid has one row and nine columns.  Constructing it should throw
+        // an IllegalArgumentException.
+        new Sudoku(new Sudoku.Cell[][]{{new Sudoku.Cell(1, false),
+                                        new Sudoku.Cell(2, false),
+                                        new Sudoku.Cell(3, false),
+                                        new Sudoku.Cell(4, false),
+                                        new Sudoku.Cell(5, false),
+                                        new Sudoku.Cell(6, false),
+                                        new Sudoku.Cell(7, false),
+                                        new Sudoku.Cell(8, false),
+                                        new Sudoku.Cell(9, false)}});
+    }
+
+
+    @Test(expectedExceptions = IllegalArgumentException.class)
+    public void testWrongNumberOfColumns()
+    {
+        // This grid has nine rows and one column.  Constructing it should throw
+        // an IllegalArgumentException.
+        new Sudoku(new Sudoku.Cell[][]{{new Sudoku.Cell(1, false)},
+                                       {new Sudoku.Cell(2, false)},
+                                       {new Sudoku.Cell(3, false)},
+                                       {new Sudoku.Cell(4, false)},
+                                       {new Sudoku.Cell(5, false)},
+                                       {new Sudoku.Cell(6, false)},
+                                       {new Sudoku.Cell(7, false)},
+                                       {new Sudoku.Cell(8, false)},
+                                       {new Sudoku.Cell(9, false)}});
+    }
+
+
+    @Test(expectedExceptions = IllegalArgumentException.class)
+    public void testCellValueTooLow()
+    {
+        new Sudoku.Cell(0, false);
+    }
+
+
+    @Test(expectedExceptions = IllegalArgumentException.class)
+    public void testCellValueTooHigh()
+    {
+        new Sudoku.Cell(10, false);
+    }
+
+
+    @Test
+    public void testToString()
+    {
+        Sudoku sudoku = SudokuTestUtils.createSudoku(new int[][]{{1, 2, 3, 4, 5, 6, 7, 8, 9},
+                                                                 {1, 2, 3, 4, 5, 6, 7, 8, 9},
+                                                                 {1, 2, 3, 4, 5, 6, 7, 8, 9},
+                                                                 {1, 2, 3, 4, 5, 6, 7, 8, 9},
+                                                                 {1, 2, 3, 4, 5, 6, 7, 8, 9},
+                                                                 {1, 2, 3, 4, 5, 6, 7, 8, 9},
+                                                                 {1, 2, 3, 4, 5, 6, 7, 8, 9},
+                                                                 {1, 2, 3, 4, 5, 6, 7, 8, 9},
+                                                                 {1, 2, 3, 4, 5, 6, 7, 8, 9}});
+        String text = sudoku.toString();
+        assert text.equals(" 1 2 3 4 5 6 7 8 9\n" +
+                           " 1 2 3 4 5 6 7 8 9\n" +
+                           " 1 2 3 4 5 6 7 8 9\n" +
+                           " 1 2 3 4 5 6 7 8 9\n" +
+                           " 1 2 3 4 5 6 7 8 9\n" +
+                           " 1 2 3 4 5 6 7 8 9\n" +
+                           " 1 2 3 4 5 6 7 8 9\n" +
+                           " 1 2 3 4 5 6 7 8 9\n" +
+                           " 1 2 3 4 5 6 7 8 9\n") : "Wrong string representation:\n" + text;
+    }
+}
diff --git a/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/sudoku/SudokuTestUtils.java b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/sudoku/SudokuTestUtils.java
new file mode 100644
index 0000000..58dc4ea
--- /dev/null
+++ b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/sudoku/SudokuTestUtils.java
@@ -0,0 +1,48 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.sudoku;
+
+/**
+ * Utility methods that help in unit tests.
+ * @author Daniel Dyer
+ */
+class SudokuTestUtils
+{
+    private SudokuTestUtils()
+    {
+        // Prevents instantiation.
+    }
+
+
+    /**
+     * Convenience method for creating a Sudoku object from a 2D array of ints.
+     * Ignores which cells are fixed and which are not.
+     * @param values A 9x9 2-dimensional array that contains values (1-9) for
+     * each of the cells in a Sudoku grid.
+     */
+    public static Sudoku createSudoku(int[][] values)
+    {
+        Sudoku.Cell[][] cells = new Sudoku.Cell[Sudoku.SIZE][Sudoku.SIZE];
+        for (int i = 0; i < Sudoku.SIZE; i++)
+        {
+            for (int j = 0; j < Sudoku.SIZE; j++)
+            {
+                cells[i][j] = new Sudoku.Cell(values[i][j], false);
+            }
+        }
+        return new Sudoku(cells);
+    }
+}
diff --git a/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/sudoku/SudokuVerticalCrossoverTest.java b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/sudoku/SudokuVerticalCrossoverTest.java
new file mode 100644
index 0000000..4f430be
--- /dev/null
+++ b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/sudoku/SudokuVerticalCrossoverTest.java
@@ -0,0 +1,64 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.sudoku;
+
+import java.util.Arrays;
+import java.util.List;
+import org.testng.annotations.Test;
+import org.uncommons.watchmaker.examples.ExamplesTestUtils;
+import org.uncommons.watchmaker.framework.EvolutionaryOperator;
+
+/**
+ * Unit test for Sudoku cross-over operator.
+ * @author Daniel Dyer
+ */
+public class SudokuVerticalCrossoverTest
+{
+    /**
+     * Ensures that the simplest configuration (a single cross-over point)
+     * works as expected.
+     */
+    @Test
+    public void testSinglePointCrossover()
+    {
+        EvolutionaryOperator<Sudoku> crossover = new SudokuVerticalCrossover();
+        int[] forwards = {1, 2, 3, 4, 5, 6, 7, 8, 9};
+        int[] backwards = {9, 8, 7, 6, 5, 4, 3, 2, 1};
+        int[][] parent1 = new int[Sudoku.SIZE][];
+        int[][] parent2 = new int[Sudoku.SIZE][];
+        for (int i = 0; i < Sudoku.SIZE; i++)
+        {
+            parent1[i] = forwards;
+            parent2[i] = backwards;
+        }
+        List<Sudoku> population = Arrays.asList(SudokuTestUtils.createSudoku(parent1),
+                                                SudokuTestUtils.createSudoku(parent2));
+        population = crossover.apply(population, ExamplesTestUtils.getRNG());
+        assert population.size() == 2 : "Population size changed after cross-over.";
+        Sudoku offspring1 = population.get(0);
+        Sudoku offspring2 = population.get(1);
+        // Two groups of rows should be different from each other (they come from different parents).
+        assert !Arrays.equals(offspring1.getRow(0), offspring1.getRow(8))
+            : "Row 0 should not match row 8.";
+        assert !Arrays.equals(offspring2.getRow(0), offspring2.getRow(8))
+            : "Row 0 should not match row 8.";
+        // The two offspring should have inherited different rows.
+        assert !Arrays.equals(offspring1.getRow(0), offspring2.getRow(0))
+            : "Offspring 1 row 0 should not match offspring 2 row 0.";
+        assert !Arrays.equals(offspring1.getRow(8), offspring2.getRow(8))
+            : "Offspring 1 row 8 should not match offspring 2 row 8.";
+    }
+}
diff --git a/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/sudoku/SudokuViewTest.java b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/sudoku/SudokuViewTest.java
new file mode 100644
index 0000000..999a92a
--- /dev/null
+++ b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/sudoku/SudokuViewTest.java
@@ -0,0 +1,117 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.sudoku;
+
+import java.awt.BorderLayout;
+import javax.swing.JFrame;
+import org.fest.swing.core.BasicRobot;
+import org.fest.swing.core.Robot;
+import org.fest.swing.data.TableCell;
+import org.fest.swing.fixture.FrameFixture;
+import org.fest.swing.fixture.JTableCellFixture;
+import org.testng.annotations.AfterMethod;
+import org.testng.annotations.BeforeMethod;
+import org.testng.annotations.Test;
+
+/**
+ * Unit test for the {@link SudokuView} class.
+ * @author Daniel Dyer
+ */
+public class SudokuViewTest
+{
+    private static final String[] TEST_PUZZLE = {"4.5...9.7",
+                                                 ".2..9..6.",
+                                                 "39.6.7.28",
+                                                 "9..3.2..6",
+                                                 "7..9.6..3",
+                                                 "5..4.8..1",
+                                                 "28.1.5.49",
+                                                 ".7..3..8.",
+                                                 "6.4...3.2"};
+
+    private Robot robot;
+
+    @BeforeMethod(groups = "display-required")
+    public void prepare()
+    {
+        robot = BasicRobot.robotWithNewAwtHierarchy();
+    }
+
+
+    @AfterMethod(groups = "display-required")
+    public void cleanUp()
+    {
+        robot.cleanUp();
+        robot = null;
+    }
+
+    
+    @Test(groups = "display-required")
+    public void testDisplayPuzzle()
+    {
+        SudokuView view = new SudokuView();
+        JFrame frame = new JFrame();
+        frame.add(view, BorderLayout.CENTER);
+        FrameFixture frameFixture = new FrameFixture(robot, frame);
+        frame.setSize(400, 400);
+        frame.validate();
+
+        frameFixture.show();
+        view.setPuzzle(TEST_PUZZLE);
+
+        // Check a non-empty cell.
+        JTableCellFixture cell1 = frameFixture.table().cell(TableCell.row(0).column(0));
+        cell1.requireEditable();
+        cell1.requireValue("4");
+
+        // And an empty cell.
+        JTableCellFixture cell2 = frameFixture.table().cell(TableCell.row(0).column(1));
+        cell2.requireEditable();
+        cell2.requireValue("");
+    }
+
+
+    @Test(groups = "display-required")
+    public void testDisplaySolution()
+    {
+        SudokuView view = new SudokuView();
+        JFrame frame = new JFrame();
+        frame.add(view, BorderLayout.CENTER);
+        FrameFixture frameFixture = new FrameFixture(robot, frame);
+        frame.setSize(400, 400);
+        frame.validate();
+
+        frameFixture.show();
+        Sudoku sudoku = SudokuTestUtils.createSudoku(new int[][]
+        {
+            {1, 2, 8, 5, 4, 3, 9, 6, 7},
+            {7, 6, 4, 9, 2, 8, 5, 1, 3},
+            {3, 9, 5, 7, 6, 1, 2, 4, 8},
+            {6, 1, 9, 4, 8, 5, 7, 3, 2},
+            {5, 8, 3, 6, 7, 2, 1, 9, 4},
+            {4, 7, 2, 3, 1, 9, 8, 5, 6},
+            {8, 5, 1, 2, 3, 6, 4, 7, 9},
+            {9, 4, 6, 8, 5, 7, 3, 2, 1},
+            {2, 3, 7, 1, 9, 4, 6, 8, 5}
+        });
+        view.setSolution(sudoku);
+
+        JTableCellFixture cell1 = frameFixture.table().cell(TableCell.row(0).column(0));
+        cell1.requireNotEditable();
+        cell1.requireValue("1");
+    }
+
+}
diff --git a/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/travellingsalesman/BruteForceTravellingSalesmanTest.java b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/travellingsalesman/BruteForceTravellingSalesmanTest.java
new file mode 100644
index 0000000..ee7a144
--- /dev/null
+++ b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/travellingsalesman/BruteForceTravellingSalesmanTest.java
@@ -0,0 +1,51 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.travellingsalesman;
+
+import java.util.Arrays;
+import java.util.List;
+import org.testng.annotations.Test;
+
+/**
+ * Test for the brute force solution to the travelling salesman
+ * problem.
+ * @author Daniel Dyer
+ */
+public class BruteForceTravellingSalesmanTest
+{
+    /**
+     * Make sure that the brute force implementation returns the correct result.
+     */
+    @Test
+    public void testEvaluation()
+    {
+        DistanceLookup data = new TestDistances();
+        TravellingSalesmanStrategy strategy = new BruteForceTravellingSalesman(data);
+        List<String> cities = Arrays.asList("City1", "City2", "City3", "City4");        
+        List<String> route = strategy.calculateShortestRoute(cities, null);
+        assert route.size() == 4 : "Route is wrong length: " + route.size();
+        assert route.contains("City1") : "Route does not contain City1.";
+        assert route.contains("City2") : "Route does not contain City2.";
+        assert route.contains("City3") : "Route does not contain City3.";
+        assert route.contains("City4") : "Route does not contain City4.";
+        double distance = 0;
+        distance += data.getDistance(route.get(0), route.get(1));
+        distance += data.getDistance(route.get(1), route.get(2));
+        distance += data.getDistance(route.get(2), route.get(3));
+        distance += data.getDistance(route.get(3), route.get(0));
+        assert (long) distance == 47 : "Incorrect shortest route: " + distance;
+    }
+}
diff --git a/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/travellingsalesman/EuropeanDistanceLookupTest.java b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/travellingsalesman/EuropeanDistanceLookupTest.java
new file mode 100644
index 0000000..debdc96
--- /dev/null
+++ b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/travellingsalesman/EuropeanDistanceLookupTest.java
@@ -0,0 +1,65 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.travellingsalesman;
+
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Queue;
+import org.testng.annotations.Test;
+
+/**
+ * Unit test for the distance look-ups for European cities that is used by
+ * the Travelling Salesman applet.
+ * @author Daniel Dyer
+ */
+public class EuropeanDistanceLookupTest
+{
+    /**
+     * Check to make sure that each city's distance to itself is zero.
+     */
+    @Test
+    public void testSelfDistances()
+    {
+        DistanceLookup europe = new EuropeanDistanceLookup();
+        List<String> cities = europe.getKnownCities();
+        for (String city : cities)
+        {
+            assert europe.getDistance(city, city) == 0 : city + " distance to self is non-zero.";
+        }
+    }
+
+
+    /**
+     * Check to make sure that for every pair of cities, the distance in one
+     * direction is equal to the distance in the other direction.
+     */
+    @Test
+    public void testReturnDistances()
+    {
+        DistanceLookup europe = new EuropeanDistanceLookup();
+        Queue<String> cities = new LinkedList<String>(europe.getKnownCities());
+        while (!cities.isEmpty())
+        {
+            String startCity = cities.remove();
+            for(String city : cities)
+            {
+                int outDistance = europe.getDistance(startCity, city);
+                int returnDistance = europe.getDistance(city, startCity);
+                assert outDistance == returnDistance : "Return distance mismatch for " + startCity + " and " + city;
+            }
+        }
+    }
+}
diff --git a/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/travellingsalesman/EvolutionaryTravellingSalesmanTest.java b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/travellingsalesman/EvolutionaryTravellingSalesmanTest.java
new file mode 100644
index 0000000..c2ece30
--- /dev/null
+++ b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/travellingsalesman/EvolutionaryTravellingSalesmanTest.java
@@ -0,0 +1,95 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.travellingsalesman;
+
+import java.util.Arrays;
+import java.util.List;
+import org.testng.annotations.Test;
+import org.uncommons.watchmaker.framework.selection.TruncationSelection;
+
+/**
+ * Unit test for the evolutionary approach to the travelling salesman problem.
+ * This test does not check that the correct result is returned (we would need
+ * to run the full evolutionary algorithm for that, and even then optimality
+ * is not guaranteed).  This just ensures that nothing invalid happens and
+ * provides coverage for the classes involved.
+ * @author Daniel Dyer
+ */
+public class EvolutionaryTravellingSalesmanTest
+{
+    private final DistanceLookup data = new TestDistances();
+
+    /**
+     * Ensure that the algorithm behaves when configured to use mutation.
+     */
+    @Test
+    public void testWithMutation()
+    {
+        TravellingSalesmanStrategy strategy = new EvolutionaryTravellingSalesman(data,
+                                                                                 new TruncationSelection(0.5),
+                                                                                 10, // Small population.
+                                                                                 0, // No elitism.
+                                                                                 3, // Only a few generations.
+                                                                                 false, // Cross-over.
+                                                                                 true); // Mutation.
+        List<String> cities = Arrays.asList("City1", "City2", "City3", "City4");
+        List<String> route = strategy.calculateShortestRoute(cities, null);
+        assert route.size() == 4 : "Route is wrong length: " + route.size();
+        assert route.contains("City1") : "Route does not contain City1.";
+        assert route.contains("City2") : "Route does not contain City2.";
+        assert route.contains("City3") : "Route does not contain City3.";
+        assert route.contains("City4") : "Route does not contain City4.";
+    }
+
+
+    /**
+     * Ensure that the algorithm behaves when configured to use cross-over.
+     */
+    @Test
+    public void testWithCrossover()
+    {
+        TravellingSalesmanStrategy strategy = new EvolutionaryTravellingSalesman(data,
+                                                                                 new TruncationSelection(0.5),
+                                                                                 10, // Small population.
+                                                                                 0, // No elitism.
+                                                                                 3, // Only a few generations.
+                                                                                 true, // Cross-over
+                                                                                 false); // Mutation.
+        List<String> cities = Arrays.asList("City1", "City2", "City3", "City4");
+        List<String> route = strategy.calculateShortestRoute(cities, null);
+        assert route.size() == 4 : "Route is wrong length: " + route.size();
+        assert route.contains("City1") : "Route does not contain City1.";
+        assert route.contains("City2") : "Route does not contain City2.";
+        assert route.contains("City3") : "Route does not contain City3.";
+        assert route.contains("City4") : "Route does not contain City4.";
+    }
+
+
+    /**
+     * The strategy must ensure that at least one of cross-over or mutation is chosen.
+     */
+    @Test(expectedExceptions = IllegalArgumentException.class)
+    public void testNoEvolution()
+    {
+        new EvolutionaryTravellingSalesman(data,
+                                           new TruncationSelection(0.5),
+                                           10,
+                                           0,
+                                           3,
+                                           false,
+                                           false); // Should throw an IllegalArgumentException as no operators are enabled.
+    }
+}
diff --git a/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/travellingsalesman/ItineraryPanelTest.java b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/travellingsalesman/ItineraryPanelTest.java
new file mode 100644
index 0000000..9f2244d
--- /dev/null
+++ b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/travellingsalesman/ItineraryPanelTest.java
@@ -0,0 +1,91 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.travellingsalesman;
+
+import java.awt.BorderLayout;
+import java.util.Collection;
+import javax.swing.JFrame;
+import org.fest.swing.core.BasicRobot;
+import org.fest.swing.core.Robot;
+import org.fest.swing.fixture.FrameFixture;
+import org.testng.annotations.AfterMethod;
+import org.testng.annotations.BeforeMethod;
+import org.testng.annotations.Test;
+
+/**
+ * Basic unit test for the {@link ItineraryPanel} class.  Makes sure that the
+ * buttons operate as expected so that the right cities are returned.
+ * @author Daniel Dyer
+ */
+public class ItineraryPanelTest
+{
+    private static final TestDistances CITIES = new TestDistances();
+
+    private Robot robot;
+
+    @BeforeMethod
+    public void prepare()
+    {
+        robot = BasicRobot.robotWithNewAwtHierarchy();
+    }
+
+
+    @AfterMethod
+    public void cleanUp()
+    {
+        robot.cleanUp();
+        robot = null;
+    }
+    
+
+    @Test(groups = "display-required") // Will fail if run in a headless environment.
+    public void testSelectAll()
+    {
+        ItineraryPanel itineraryPanel = new ItineraryPanel(CITIES.getKnownCities());
+        JFrame frame = new JFrame();
+        frame.add(itineraryPanel, BorderLayout.CENTER);
+        FrameFixture frameFixture = new FrameFixture(robot, frame);
+        frame.setSize(100, 300);
+        frame.validate();
+        frame.setVisible(true);
+        assert itineraryPanel.getSelectedCities().isEmpty() : "Should be no cities selected initially.";
+        frameFixture.button("All").click();
+        Collection<String> selectedCities = itineraryPanel.getSelectedCities();
+        assert selectedCities.size() == CITIES.getKnownCities().size()
+            : "All cities should be selected after button click.";
+    }
+
+
+    @Test(groups = "display-required", // Will fail if run in a headless environment.
+          dependsOnMethods = "testSelectAll")
+    public void testSelectNone()
+    {
+        ItineraryPanel itineraryPanel = new ItineraryPanel(CITIES.getKnownCities());
+        JFrame frame = new JFrame();
+        frame.add(itineraryPanel, BorderLayout.CENTER);
+        FrameFixture frameFixture = new FrameFixture(robot, frame);
+        frame.setSize(100, 300);
+        frame.validate();
+        frame.setVisible(true);
+        frameFixture.button("All").click();
+        Collection<String> selectedCities = itineraryPanel.getSelectedCities();
+        assert selectedCities.size() == CITIES.getKnownCities().size()
+            : "All cities should be selected after all button click.";
+        frameFixture.button("None").click();
+        assert itineraryPanel.getSelectedCities().isEmpty()
+            : "No cities should be selected after clear button is clicked.";
+    }
+}
diff --git a/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/travellingsalesman/RouteEvaluatorTest.java b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/travellingsalesman/RouteEvaluatorTest.java
new file mode 100644
index 0000000..b6ca0ee
--- /dev/null
+++ b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/travellingsalesman/RouteEvaluatorTest.java
@@ -0,0 +1,70 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.travellingsalesman;
+
+import java.util.Arrays;
+import java.util.List;
+import org.testng.annotations.Test;
+
+/**
+ * Unit test for the route evaluator used by both Travelling Salesman
+ * implementations.  Checks to make sure that route distances are
+ * calculated correctly.
+ * @author Daniel Dyer
+ */
+public class RouteEvaluatorTest
+{
+    /**
+     * Test different routes to make sure the distances are calculated correctly.
+     */
+    @Test
+    public void testDistanceCalculations()
+    {
+        RouteEvaluator evaluator = new RouteEvaluator(new TestDistances());
+
+        List<String> route1 = Arrays.asList("City4", "City1", "City3", "City2");
+        // Expected distance is sum of distances between adjacent cities on route
+        // including returning to the start city.
+        int expectedDistance1 = 8 + 5 + 13 + 21;
+        int actualDistance1 = (int) evaluator.getFitness(route1, null);
+        assert actualDistance1 == expectedDistance1 : "Distance should be " + expectedDistance1 + ", was " + actualDistance1;
+
+        List<String> route2 = Arrays.asList("City3", "City4", "City2", "City1");
+        // Expected distance is sum of distances between adjacent cities on route
+        // including returning to the start city.
+        int expectedDistance2 = 34 + 21 + 3 + 5;
+        int actualDistance2 = (int) evaluator.getFitness(route2, null);
+        assert actualDistance2 == expectedDistance2 : "Distance should be " + expectedDistance2 + ", was " + actualDistance2;
+    }
+
+
+    /**
+     * Make sure the route evaluator works for end cases.
+     */
+    @Test
+    public void testSingleCityRoute()
+    {
+        RouteEvaluator evaluator = new RouteEvaluator(new TestDistances());
+
+        List<String> route = Arrays.asList("City1");
+        // Expected distance is sum of distances between adjacent cities on route
+        // including returning to the start city.
+        int distance = (int) evaluator.getFitness(route, null);
+        assert distance == 0 : "Distance should be 0, was " + distance;        
+    }
+
+
+}
diff --git a/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/travellingsalesman/StrategyPanelTest.java b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/travellingsalesman/StrategyPanelTest.java
new file mode 100644
index 0000000..00519d9
--- /dev/null
+++ b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/travellingsalesman/StrategyPanelTest.java
@@ -0,0 +1,119 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.travellingsalesman;
+
+import java.awt.BorderLayout;
+import javax.swing.JFrame;
+import org.fest.swing.core.BasicRobot;
+import org.fest.swing.core.Robot;
+import org.fest.swing.fixture.FrameFixture;
+import org.testng.annotations.AfterMethod;
+import org.testng.annotations.BeforeMethod;
+import org.testng.annotations.Test;
+
+/**
+ * Basic unit test for the {@link StrategyPanel} used by the Travelling
+ * Salesman example applet.  Makes sure that it returns the correct type
+ * of solver strategy depending on the radio button settings.
+ * @author Daniel Dyer
+ */
+public class StrategyPanelTest
+{
+    private static final TestDistances CITIES = new TestDistances();
+    
+    private Robot robot;
+
+    @BeforeMethod
+    public void prepare()
+    {
+        robot = BasicRobot.robotWithNewAwtHierarchy();
+    }
+
+
+    @AfterMethod
+    public void cleanUp()
+    {
+        robot.cleanUp();
+        robot = null;
+    }
+
+    
+    @Test(groups = "display-required")
+    public void testBruteForceOption()
+    {
+        StrategyPanel strategyPanel = new StrategyPanel(CITIES);
+        JFrame frame = new JFrame();
+        frame.add(strategyPanel, BorderLayout.CENTER);
+        FrameFixture frameFixture = new FrameFixture(robot, frame);
+        frame.setSize(500, 300);
+        frame.validate();
+        frame.setVisible(true);
+        robot.waitForIdle();
+
+        // Evolution controls should be enabled by default.
+        frameFixture.panel("EvolutionPanel").requireEnabled();
+
+        frameFixture.radioButton("BruteForceOption").click();
+
+        // Evolution controls should be disabled when brute force option is selected.
+        frameFixture.panel("EvolutionPanel").requireDisabled();
+
+        TravellingSalesmanStrategy strategy = strategyPanel.getStrategy();
+        assert strategy instanceof BruteForceTravellingSalesman : "Wrong strategy class: " + strategy.getClass();
+    }
+
+
+    @Test(groups = "display-required")
+    public void testEvolutionOption()
+    {
+        StrategyPanel strategyPanel = new StrategyPanel(CITIES);
+        JFrame frame = new JFrame();
+        frame.add(strategyPanel, BorderLayout.CENTER);
+        FrameFixture frameFixture = new FrameFixture(robot, frame);
+        frame.setSize(500, 300);
+        frame.validate();
+        frame.setVisible(true);
+        robot.waitForIdle();
+
+        frameFixture.radioButton("EvolutionOption").click();
+        TravellingSalesmanStrategy strategy = strategyPanel.getStrategy();
+        assert strategy instanceof EvolutionaryTravellingSalesman : "Wrong strategy class: " + strategy.getClass();
+    }
+
+
+    @Test(groups = "display-required")
+    public void testDisablePanel()
+    {
+        StrategyPanel strategyPanel = new StrategyPanel(CITIES);
+        JFrame frame = new JFrame();
+        frame.add(strategyPanel, BorderLayout.CENTER);
+        FrameFixture frameFixture = new FrameFixture(robot, frame);
+        frame.setSize(500, 300);
+        frame.validate();
+        frame.setVisible(true);
+        robot.waitForIdle();
+
+        // Components should be enabled initially.
+        frameFixture.radioButton("EvolutionOption").requireEnabled();
+        frameFixture.panel("EvolutionPanel").requireEnabled();
+        frameFixture.radioButton("BruteForceOption").requireEnabled();
+
+        strategyPanel.setEnabled(false);
+        frameFixture.radioButton("EvolutionOption").requireDisabled();
+        frameFixture.panel("EvolutionPanel").requireDisabled();
+        frameFixture.radioButton("BruteForceOption").requireDisabled();        
+    }
+}
diff --git a/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/travellingsalesman/TestDistances.java b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/travellingsalesman/TestDistances.java
new file mode 100644
index 0000000..cc7da3a
--- /dev/null
+++ b/watchmaker/examples/src/java/test/org/uncommons/watchmaker/examples/travellingsalesman/TestDistances.java
@@ -0,0 +1,70 @@
+//=============================================================================
+// Copyright 2006-2010 Daniel W. Dyer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//=============================================================================
+package org.uncommons.watchmaker.examples.travellingsalesman;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+import java.util.TreeMap;
+
+/**
+ * Test data for travelling salesman unit tests.  The shortest route between each
+ * of the four cities in this data set is 47km.
+ */
+final class TestDistances implements DistanceLookup
+{
+    private static final Map<String, Map<String, Integer>> distances = new TreeMap<String, Map<String, Integer>>();
+    static
+    {
+        Map<String, Integer> city1 = new TreeMap<String, Integer>();
+        city1.put("City1", 0);
+        city1.put("City2", 3);
+        city1.put("City3", 5);
+        city1.put("City4", 8);
+        distances.put("City1", city1);
+
+        Map<String, Integer> city2 = new TreeMap<String, Integer>();
+        city2.put("City1", 3);
+        city2.put("City2", 0);
+        city2.put("City3", 13);
+        city2.put("City4", 21);
+        distances.put("City2", city2);
+
+        Map<String, Integer> city3 = new TreeMap<String, Integer>();
+        city3.put("City1", 5);
+        city3.put("City2", 13);
+        city3.put("City3", 0);
+        city3.put("City4", 34);
+        distances.put("City3", city3);
+
+        Map<String, Integer> city4 = new TreeMap<String, Integer>();
+        city4.put("City1", 8);
+        city4.put("City2", 21);
+        city4.put("City3", 34);
+        city4.put("City4", 0);
+        distances.put("City4", city4);
+    }
+
+    public List<String> getKnownCities()
+    {
+        return new ArrayList<String>(distances.keySet());
+    }
+
+    public int getDistance(String startingCity, String destinationCity)
+    {
+        return distances.get(startingCity).get(destinationCity);
+    }
+}