Viper-Engine-Demos is a project mainly written in Java, it's free.
Viper Engine Demos
Viper is an open source game-making library that is completely free for personal or commercial use. Written entirely in Java by Yura Zatsepin. Viper is easy to learn, extend and customize. Basic is PlayN - http://code.google.com/p/playn/
Viper includes some basic features common to many game engines or other game libraries.
Features: