public Vector2f subtract(Vector2f vec) {
        return subtract(vec, null);
    }
Subtracts the argument and returns the difference as a new instance. The
current instance is unaffected.

@param vec the vector to subtract (not null, unaffected)
@return a new Vector2f
jme3-core/src/main/java/com/jme3/math/Vector2f.java