Here are some very useful links to get information about programming the NXT in the Java Language:
- SourceForge From here, you can download the jar files as well as the brick's firmware to get you started programming in Lejos -- Java for the Mindstorms NXT brick
- Setup Tutorial From this website, you can learn how to properly set up your brick with the firmware, and correctly get Eclipse (a Java development environment) working properly
- Forum In this forum, you can communicate with other developers who use Lejos to program the NXT brick