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sources/main/java/javax/annotation/concurrent/Immutable.java

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+/*
+ * Copyright (c) 2005 Brian Goetz
+ * Released under the Creative Commons Attribution License
+ *   (http://creativecommons.org/licenses/by/2.5)
+ * Official home: http://www.jcip.net
+ */
+package javax.annotation.concurrent;
+
+import java.lang.annotation.Documented;
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+/**
+ * The class to which this annotation is applied is immutable. This means that
+ * its state cannot be seen to change by callers. Of necessity this means that
+ * all public fields are final, and that all public final reference fields refer
+ * to other immutable objects, and that methods do not publish references to any
+ * internal state which is mutable by implementation even if not by design.
+ * Immutable objects may still have internal mutable state for purposes of
+ * performance optimization; some state variables may be lazily computed, so
+ * long as they are computed from immutable state and that callers cannot tell
+ * the difference.
+ * <p>
+ * Immutable objects are inherently thread-safe; they may be passed between
+ * threads or published without synchronization.
+ */
+@Documented
+@Target(ElementType.TYPE)
+@Retention(RetentionPolicy.CLASS)
+public @interface Immutable {
+}