public void removeCollideWithGroup(int collisionGroup) {
        this.collisionGroupsMask = this.collisionGroupsMask & ~collisionGroup;
    }
Remove a group from the list this object collides with.

@param collisionGroup the groups to remove, ORed together (bitmask)
jme3-jbullet/src/main/java/com/jme3/bullet/collision/PhysicsCollisionObject.java