VecmathUtil { static Vector2d negate(final Tuple2d vector) { return new Vector2d(-vector.x, -vector.y); } private  VecmathUtil();   }
@Test public void testNegate() throws Exception { Vector2d vector = VecmathUtil.negate(new Vector2d(4, 2)); assertThat(vector.x, closeTo(-4d, 0.01)); assertThat(vector.y, closeTo(-2d, 0.01)); }