VecmathUtil { static Vector2d sum(final Tuple2d a, final Tuple2d b) { return new Vector2d(a.x + b.x, a.y + b.y); } private  VecmathUtil();   }
@Test public void testSum() throws Exception { Vector2d vector = VecmathUtil.sum(new Vector2d(4, 2), new Vector2d(2, 5)); assertThat(vector.x, closeTo(6d, 0.01)); assertThat(vector.y, closeTo(7d, 0.01)); }