How can I turn my Java 3D application into a cross-platform screensaver?

java.net offers early access to the SaverBeans Screensaver SDK (https://jdic.dev.java.net/documentation/incubator/screensaver/ for just such a purpose. It doesn't work on the Mac, but does work on Linux, Solaris, and Windows XP.

There are also some screensavers available for download from https://screensavers.dev.java.net/ via the SaverBeans Screensaver Pack.