The Utilis Project is a library of helpful Java classes.  The entire Utilis Project is open source.  You can find the downloads at the Downloads page.

Utilis and UtiliGame
The Utilis Project consists of two main branches: Utilis and UtiliGame.

Utilis contains helpful class for doing complex mathematical functions, disk I/O, serialization of classes, and managing arrays.  Utilis expands on the Java API and provides a hegher level, simpler interface to it.  Utilis contains functions we think almost all developers would have a need for.  Utilis is designed to make doing repetitive tasks easier.  Utilis is still in beta, and many features may be missing.  Utilis is not by any stretch complete, and the 1.0 version will contain many, many more features.

UtiliGame is a lightweight Java game engine.  UtiliGame is built over Utilis and requires Utilis as a dependency   It supports tiles, non tiled objects, collision detection, custom collision boxes, and (in the future) built-in saving.  Utilis is designed to provide the basic tools a game developer needs, but to not overwhelm them with code.