mhawk, are you developing programs, or just running a java application?
ashwinipatankar gave some good tips for either case, but you also need to verify that java is installed on your machine. you can check just by typing on the command line:
If you get "command not found", you will need to install java. The procedure depends on which distribution you're using. You could also try installing java using the installer from oracle
, but I recommend using the package manager for your distribution.
You can also try out openJDK
, which should also be available via your package manager.