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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
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+//=============================================================================
+// 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;
+    }
+}