--- old/src/share/classes/java/util/Optional.java 2013-12-03 14:17:02.837080173 -0800 +++ new/src/share/classes/java/util/Optional.java 2013-12-03 14:17:02.609080162 -0800 @@ -40,6 +40,11 @@ * {@link #ifPresent(java.util.function.Consumer) ifPresent()} (execute a block * of code if the value is present). * + *
This is a value-based
+ * class; use of identity-sensitive operations (including reference equality
+ * ({@code ==}), identity hash code, or synchronization) on instances of
+ * {@code Optional} may have unpredictable effects and should be avoided.
+ *
* @since 1.8
*/
public final class Optional