Hi,
with the help of the Launch4J tool I have succeeded to
make a windows screensaver out of a java application that
shows a nice animation using geometric optics in a crystal
lattice. As far as I know this is the only way to
do it as the java screensaver framework initated by sun has
been given up years before.

FroZenLight - Homepage

The screensaver is at the bottom of the page. In the
middle of the page you find a java web start link
showing the same animation.

Zoltan