Tyrannus
Tyrannus is a Chess GUI and Engine built in Java.
..., just send me a message and we can see about that.
Latest Update:
The Engine beats me easily now, and I have pre-programmed 4 different difficulties into the release of version 2.0. The idea is that 1.0 was a chess app, and 2.0 is a chess engine. Hope you enjoy playing against the engine! Good luck.