@Override
    public BoundingVolume merge(BoundingVolume volume) {
        return mergeLocal(volume);
    }
<code>merge</code> combines this bounding box locally with a second
bounding volume. The result contains both the original box and the second
volume.

@param volume the bounding volume to combine with this box (or null) (not
altered)
@return this box (with its components modified) or null if the second
volume is of some type other than AABB or Sphere
jme3-core/src/main/java/com/jme3/bounding/BoundingBox.java