There is a new 2D physics engine available on sourceforge. The name of the project is "Foundational Physics," which has been my high school senior project this semester. It was built from the ground up to be a flexible physics engine that is relatively easy for programmers to implement. I have not experimented much with the other physics engines available in Java, so if anyone has the time I would appreciate some feedback.
The sourceforge.net address is: http://sourceforge.net/projects/foundationphys