"Robocode is an easy-to-use robotics battle simulator that runs across all platforms supporting Java 2. You create a robot, put it onto a battlefield, and let it battle to the bitter end against robots created by other developers. Robocode comes with a set of pre-fab opponents to get you started, but once you outgrow them, you can enter your creation against the world's best in one of the leagues being formed worldwide.

Each Robocode participant creates his or her own robot using elements of the Java language, enabling a range of developers – from rank beginners to advanced hackers – to participate in the fun. Beginning Java developers can learn the basics: calling API code, reading Javadocs, inheritance, inner classes, event handling, and the like. Advanced developers can tune their programming skill in a global challenge to build the best-of-breed software robot. At the time of this writing, a Robocode robot is a graphical tank. [The] robot has a rotating gun, and on top of the gun is a rotating radar. The robot vehicle, the gun, and the radar can all rotate independently.

For a project that debuted as recently as July 12, 2001, Robocode's climb to fame is nothing short of phenomenal. While the latest version available has yet to hit 1.0 (at the time of writing it is version 0.98.2), it is already becoming a very popular pastime on university campuses and corporate computers throughout the world. Robocode leagues (or roboleagues), in which people pit their custom creations against each other over the Internet, are springing up fast. University professors are tapping Robocode's educational properties and have incorporated it into their computer science curriculum. Robocode user groups, discussion lists, FAQs, tutorials, and Webrings can be found throughout the Internet. Evidently, Robocode has filled a void in the popular gaming and educational arena – supplying a simple, fun, non-intimidating, yet competitive way for students and midnight engineers to unleash their creative energy and potentially fulfill their fantasy to conquer the world." If you are learning Java, Robocode is one of the best ways to learn this powerful language. Even if you're not interested in Java but are in programming games in general, Robocode will provide hours of entertainment – while equipping you with knowledge about Java that may come in handy whenever you want to build a website. Two thumbs up, way up!

Note: You might want to head on over to the official site for the most up-to-date information, downloads etc. The two other sites given in the links below are both inactive.