Desktop/Android/HTML5/iOS Java game development framework
A simple cross-platform game engine for creating old-school 2D games
Arianne is an engine to develop multiplayer online games like Stendhal
Java Settlers
8-bit Graphical API for Java
Source code of the chapters of the book 3D Game Development with LWJGL
CSG for jMonkey
Example code for creating a 2D platform game in Java.
X3D Prototypes for the SMUOS Component
Java Gamepad API for multiple platforms
Open Source Virtual World and MMOG Development Platform
AMOS BASIC reimplementation in Java
A cross-platform Java 2D graphics library using OpenGL.