@Override
	public ElementDistance<Point2> distance() {
		return (u, v, i) -> i == 0 ? u.x() - v.x() : u.y() - v.y();
	}
Return the <em>y</em> value of the point.

@return the <em>y</em> value of the point
jenetics.ext/src/test/java/io/jenetics/ext/moea/Point2.java