protected void postRebuild() {
        rBody.setUserPointer(this);
        if (mass == 0.0f) {
            rBody.setCollisionFlags(rBody.getCollisionFlags() | CollisionFlags.STATIC_OBJECT);
        } else {
            rBody.setCollisionFlags(rBody.getCollisionFlags() & ~CollisionFlags.STATIC_OBJECT);
        }
    }
Builds/rebuilds the physics body when parameters have changed
jme3-jbullet/src/main/java/com/jme3/bullet/objects/PhysicsRigidBody.java