Add @NotNull, @Nullable, and @IntDef/@StringDef annotations

This changeset adds some annotations for recording whether a
method return value or method parameter can be null (@Nullable),
can never be null (@NotNull), or must be an integer enum or flag
using one of the given constants.

Change-Id: Ic932592ea3bac781c1df364447c57042461333c5

4 files changed, 195 insertions, 0 deletions

diff --git a/core/java/android/annotation/IntDef.java b/core/java/android/annotation/IntDef.java
new file mode 100644
index 0000000..0c4e5a5
--- /dev/null
+++ b/core/java/android/annotation/IntDef.java
@@ -0,0 +1,65 @@
+/*
+ * Copyright (C) 2013 The Android Open Source Project
+ *
+ * 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 android.annotation;
+
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+import static java.lang.annotation.ElementType.ANNOTATION_TYPE;
+import static java.lang.annotation.ElementType.FIELD;
+import static java.lang.annotation.ElementType.METHOD;
+import static java.lang.annotation.ElementType.PARAMETER;
+import static java.lang.annotation.RetentionPolicy.CLASS;
+import static java.lang.annotation.RetentionPolicy.SOURCE;
+
+/**
+ * Denotes that the annotated element of integer type, represents
+ * a logical type and that its value should be one of the explicitly
+ * named constants. If the {@link #flag()} attribute is set to true,
+ * multiple constants can be combined.
+ * <p>
+ * Example:
+ * <pre>{@code
+ *  &#64;Retention(CLASS)
+ *  &#64;IntDef(&#123;NAVIGATION_MODE_STANDARD, NAVIGATION_MODE_LIST, NAVIGATION_MODE_TABS&#125;)
+ *  public &#64;interface NavigationMode &#123;&#125;
+ *  public static final int NAVIGATION_MODE_STANDARD = 0;
+ *  public static final int NAVIGATION_MODE_LIST = 1;
+ *  public static final int NAVIGATION_MODE_TABS = 2;
+ *  ...
+ *  public abstract void setNavigationMode(&#64;NavigationMode int mode);
+ *  &#64;NavigationMode
+ *  public abstract int getNavigationMode();
+ * }</pre>
+ * For a flag, set the flag attribute:
+ * <pre>{@code
+ *  &#64;IntDef(
+ *      flag = true
+ *      value = &#123;NAVIGATION_MODE_STANDARD, NAVIGATION_MODE_LIST, NAVIGATION_MODE_TABS&#125;)
+ * }</pre>
+ *
+ * @hide
+ */
+@Retention(CLASS)
+@Target({ANNOTATION_TYPE})
+public @interface IntDef {
+    /** Defines the allowed constants for this element */
+    long[] value() default {};
+
+    /** Defines whether the constants can be used as a flag, or just as an enum (the default) */
+    boolean flag() default false;
+}
diff --git a/core/java/android/annotation/NonNull.java b/core/java/android/annotation/NonNull.java
new file mode 100644
index 0000000..8e604f0
--- /dev/null
+++ b/core/java/android/annotation/NonNull.java
@@ -0,0 +1,34 @@
+/*
+ * Copyright (C) 2013 The Android Open Source Project
+ *
+ * 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 android.annotation;
+
+import java.lang.annotation.Retention;
+import java.lang.annotation.Target;
+
+import static java.lang.annotation.ElementType.FIELD;
+import static java.lang.annotation.ElementType.METHOD;
+import static java.lang.annotation.ElementType.PARAMETER;
+import static java.lang.annotation.RetentionPolicy.SOURCE;
+
+/**
+ * Denotes that a parameter, field or method return value can never be null.
+ * <p>
+ * This is a marker annotation and it has no specific attributes.
+ */
+@Retention(SOURCE)
+@Target({METHOD, PARAMETER, FIELD})
+public @interface NonNull {
+}
diff --git a/core/java/android/annotation/Nullable.java b/core/java/android/annotation/Nullable.java
new file mode 100644
index 0000000..cdba2f6
--- /dev/null
+++ b/core/java/android/annotation/Nullable.java
@@ -0,0 +1,41 @@
+/*
+ * Copyright (C) 2013 The Android Open Source Project
+ *
+ * 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 android.annotation;
+
+import java.lang.annotation.Retention;
+import java.lang.annotation.Target;
+
+import static java.lang.annotation.ElementType.FIELD;
+import static java.lang.annotation.ElementType.METHOD;
+import static java.lang.annotation.ElementType.PARAMETER;
+import static java.lang.annotation.RetentionPolicy.SOURCE;
+
+/**
+ * Denotes that a parameter, field or method return value can be null.
+ * <p>
+ * When decorating a method call parameter, this denotes that the parameter can
+ * legitimately be null and the method will gracefully deal with it. Typically
+ * used on optional parameters.
+ * <p>
+ * When decorating a method, this denotes the method might legitimately return
+ * null.
+ * <p>
+ * This is a marker annotation and it has no specific attributes.
+ */
+@Retention(SOURCE)
+@Target({METHOD, PARAMETER, FIELD})
+public @interface Nullable {
+}
diff --git a/core/java/android/annotation/StringDef.java b/core/java/android/annotation/StringDef.java
new file mode 100644
index 0000000..6b9dff4
--- /dev/null
+++ b/core/java/android/annotation/StringDef.java
@@ -0,0 +1,55 @@
+/*
+ * Copyright (C) 2013 The Android Open Source Project
+ *
+ * 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 android.annotation;
+
+import java.lang.annotation.Retention;
+import java.lang.annotation.Target;
+
+import static java.lang.annotation.ElementType.ANNOTATION_TYPE;
+import static java.lang.annotation.ElementType.FIELD;
+import static java.lang.annotation.ElementType.METHOD;
+import static java.lang.annotation.ElementType.PARAMETER;
+import static java.lang.annotation.RetentionPolicy.CLASS;
+import static java.lang.annotation.RetentionPolicy.SOURCE;
+
+/**
+ * Denotes that the annotated String element, represents a logical
+ * type and that its value should be one of the explicitly named constants.
+ * <p>
+ * Example:
+ * <pre>{@code
+ *  &#64;Retention(SOURCE)
+ *  &#64;StringDef(&#123;
+ *     POWER_SERVICE,
+ *     WINDOW_SERVICE,
+ *     LAYOUT_INFLATER_SERVICE
+ *  &#125;)
+ *  public &#64;interface ServiceName &#123;&#125;
+ *  public static final String POWER_SERVICE = "power";
+ *  public static final String WINDOW_SERVICE = "window";
+ *  public static final String LAYOUT_INFLATER_SERVICE = "layout_inflater";
+ *  ...
+ *  public abstract Object getSystemService(&#64;ServiceName String name);
+ * }</pre>
+ *
+ * @hide
+ */
+@Retention(CLASS)
+@Target({ANNOTATION_TYPE})
+public @interface StringDef {
+    /** Defines the allowed constants for this element */
+    String[] value() default {};
+}