Packages
java.io Input/Output support (see josx.rcxcomm).
java.lang Core Java classes
java.net  
java.util Utilities
javax.servlet.http A Web Server for lejos
josx.platform.rcx Access to RCX sensors, motors, etc.
josx.rcxcomm RCX communication with the PC
josx.rcxcomm.remotecontrol  
josx.robotics Robotics classes
josx.util More utility classes