Simon posted a short summary of the most important additions to JDK 1.5. Of those, Generics, (ie., templates) Autoboxing (automatic conversion of primitive types to and from their reference type equivalent) and Type-safe Enumerations are the most useful, and will IMO vastly improve the readability and development of Java code. The enhanced for-loop, a simple way of iterating through collections, is slightly confusing I think (as it always happens when you "overload" keywords in this way), but useful nonetheless.