I'm looking to do some physics simulations and I need fast rendering in Java.
I've run into performance issues with Java2d in the past, so what are the fast alternatives? Is JOGL significantly faster than Java2d?
My experience with Java2D is that it can be very fast, if you follow the rules. I had an application that went from 90% CPU to less than 5% CPU just by changing a few simple things. Using large transparent PNG's is a no no, for example.
A very good resource is the Java-Gaming.org forums: a lot of people, including the Sun 2D specialists, hang out there and provide many examples and solutions to performance issues for 2D drawing.
See: http://www.javagaming.org/ and then the topic "Performance Tuning".