// The new way: works in Java 5.0+.  Interface takes a type parameter.

class Pair implements Comparable<Pair> {
    Double x, y;
    
    public Pair(double x, double y) {
        this.x = new Double(x);
        this.y = new Double(y);
    }

    public int compareTo(Pair other) {
        if ( this.x.equals(other.x) ) {
            return this.y.compareTo(other.y);
        } else {
            return this.x.compareTo(other.x);
        }
    }
}