J2SE 5.0 has just been released.
Some highlights of J2SE 5.0:
* New language updates: Metadata, Generics, Enumerated types, Autoboxing of primitive types
* New JVM Monitoring and Management API
* Improved out-of-box performance
* New (but compatible) default Java look and feel
More details can be found in "J2SE 5.0 in a Nutshell".
Download it here.