Some days ago, JGAP 2.6 has been released. JGAP is a genetic algorithms package, which is easy to use and which is delivered with ready-to-use components, such as genetic operators, selectors and examples.
Try it out now!
In the CVS you already find code to solve problems using Genetic Programming (see directory gp-src).
Feedback is very welcome :-)
PS: The German junit book references JGAP several times when it comes to sample projects utilizing JUnit.