Some guys from the Eindhoven University of Technology have created a tutorial that provides step-by-step instructions for the installation and configuration of leJOS NXJ. leJOS NXJ is a Java platform that enables you to write Java programs for the LEGO MINDSTORMS NXT and run them on the brick.
The tutorial also shows how to use the popular IDE Eclipse for that.
Hence, if you are into Object Oriented Programming when it comes to your NXT, check it out.
Thanks, Christoph and Hu!