JPhotoBrush Pro is an Award Winning Multi-Platform Image Editing/
Enhancement/ Retouch Application written in Java providing various
filters, effects and transformation with user friendly interface.
Offering a phenomenal range of adjustment for most effects, you will
find many features not found on expensive commercial editors. It has
been successfully tested in many operating systems. It is friendly
enough for the casual user who wants to enhance family photographs,
yet powerful enough for some professional graphics.
It isn't certainly just another run-of-the mill image editor!!!

Check it out at :

http://www.jphotobrushpro.com .

It also has a Plugins interface specification which can be used by
Java programmers to develop Photo effect plugins / image format
plugins.

There are yet ton of effects / features to be included . Registered
users get free upgrades for a year.