This week's giveaway is in the EJB and other Java EE Technologies forum. We're giving away four copies of EJB 3 in Action and have Debu Panda, Reza Rahman, Ryan Cuprak, and Michael Remijan on-line! See this thread for details.
Only if you
a) do not use any class, method or field that was introduced in Java 6; these will have a "Since Java 1.6" inside the Javadoc pages.
b) use the -target 1.5 compiler flag to get binary compatibility. If you forget this you will get an error when running your code.