Please don't bump threads by just posting "UP!!!", it's irritating and doesn't persuade people to answer your questions.
I think it would work if you put this into your ~/.xinitrc file:
(java Game.class; sudo shutdown -h now) &
You would need to check your sudoers file allowed you to run 'sudo shutdown -h now' without a password, or provide some other way for your user to run the 'shutdown' command without needing a password.
Hope this helps,