public Vector3f addLocal(Vector3f vec) {
        if (null == vec) {
            logger.warning("Provided vector is null, null returned.");
            return null;
        }
        x += vec.x;
        y += vec.y;
        z += vec.z;
        return this;
    }
Adds the argument and returns the (modified) current instance. If the
argument is null, null is returned.

@param vec the vector to add (unaffected unless it's {@code this})
    or null for none
@return the (modified) current instance or null
jme3-core/src/main/java/com/jme3/math/Vector3f.java