Point isn't Comparable so you'll need to write your own comparator and pass it in when calling Arrays.sort. Luckily, that's not too hard:
class PointCmp implements Comparator {
int compare(Point a, Point b) {
return (a.x < b.x) ? -1 : (a.x > b.x) ? 1 : 0;
}
}
Arrays.sort(A, new PointCmp());