The Emini Physics Engine is designed for use in J2ME and Android.
It is not actively developed anymore as most Game development frameworks have access to Physics Engines. However, if you are interested in using a standalone physics Engine, this could be an option for you. The Engine itself is still state-of-the-art constraint based physics built in Java, optimized for mobile devices. It is well documented along with usages samples and comes bundled with a designer to create physics environments that can be simulated directly in the designer and loaded from the engine in code.
There are 4 versions (zip files) available for download:
The files contain the .jar file of the actual library, license, documentation, designer and sample code.
Note that the supplied license is for non-commercial use only. If you do want to realize a commercial project you can email me for such a license at firstname.lastname@example.org