Google Annotations Gallery is an exciting new Java open source library that provides ‘rich set of annotations’ for developers to express themselves. “Not only can you leave expressive remarks in your code, you can use these annotations to draw attention to your poetic endeavors. How many times have you written a palindromic or synechdochal line of code and wished you could annotate it for future readers to admire? Look no further than @Palindrome and @Synechdoche. GAG comes complete with dynamic bytecode instrumentation. By using the gag-agent.jar Java agent, you can have your annotations behavior-enforced at runtime. For e.g., if you want to ensure that a method parameter is non-zero, try @ThisHadBetterNotBe(Property.ZERO). Want to completely inhibit a method's implementation? Try @Noop,” says Google.
More info: Google Annotations Gallery