What do you mean by %PATH% variable? I'm having the same issue and I do have the JDK installed.
EDIT: Never mind, Eclipse was pointing to JRE instead of the JDK, build works fine now!
By any chance, could anyone help with with Eclipse showing "The import edu cannot be resolved" when making new FRC Simple Project. I installed
http://first.wpi.edu/FRC/java/eclipse/update/stable/ and followed
http://grantgumina.boldlygoingnowhere.org/blog/?p=61
Any help would be appreciated!