Collision Detection

[AGP]

I've implemented CollisionListener and, of course overridden void collision() and boolean requiresPolygonIDs(). I have called Object3D.addCollisionListener(listener) on both objects, and have made the code of the collision() method to be System.exit(0); to test if anything happens. But when the collision is supposed to happen, it doesn't, and the program goes on running. Am I missing something? Thanks in advance.