@Override
            public boolean contactAdded(ManifoldPoint cp, com.bulletphysics.collision.dispatch.CollisionObject colObj0,
                    int partId0, int index0, com.bulletphysics.collision.dispatch.CollisionObject colObj1, int partId1,
                    int index1) {
                System.out.println("contact added");
                return true;
            }
Has to be called from the (designated) physics thread
jme3-jbullet/src/main/java/com/jme3/bullet/PhysicsSpace.java