public void add(Object obj) {
        if (obj == null) return;
        if (obj instanceof PhysicsControl) {
            ((PhysicsControl) obj).setPhysicsSpace(this);
        } else if (obj instanceof Spatial) {
            Spatial node = (Spatial) obj;
            for (int i = 0; i < node.getNumControls(); i++) {
                if (node.getControl(i) instanceof PhysicsControl) {
                    add(node.getControl(i));
                }
            }
        } else if (obj instanceof PhysicsCollisionObject) {
            addCollisionObject((PhysicsCollisionObject) obj);
        } else if (obj instanceof PhysicsJoint) {
            addJoint((PhysicsJoint) obj);
        } else {
            throw (new UnsupportedOperationException("Cannot add this kind of object to the physics space."));
        }
    }
adds an object to the physics space
@param obj the PhysicsControl or Spatial with PhysicsControl to add
jme3-jbullet/src/main/java/com/jme3/bullet/PhysicsSpace.java