TL;DR: Apple has dropped native feature support in Java. Especially touchpad gestures are not working any longer. I wrote a library that does the job using
Since the developer preview release of OS X El Capitan, it became impossible for 99% of average computer users to install Java 6, so this was no longer an option for me. I finally decided to write a native library that will inform Java about gestures through JNI. The project works great and is hosted on GitHub.
Take a look at it here: https://github.com/mcourteaux/MultiTouch-Gestures-Java