gistfile1.txt

class Y implements Comparable<X> {
	
	int yTest;

	@Override
	public int compareTo(X o) {
		if(this.yTest < o.xTest) return -1;
		if(this.yTest > o.xTest) return 1;
		return 0;
	}
	
}

gistfile2.txt

class X implements Comparable<Y> {
	
    int xTest;
    
	@Override
	public int compareTo(Y o) {
		if(this.xTest < o.yTest) return -1;
		if(this.xTest > o.yTest) return 1;
		return 0;
	}

}

gistfile3.txt

public class Compare {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		
		X x = new X();
		x.xTest = 10;
		
		Y y = new Y();
		y.yTest = 100;
		
		System.out.println("x.compareTo(y) == -1: " + (x.compareTo(y) == -1)); //True
		System.out.println("y.compareTo(x) == 1: " + (y.compareTo(x) == 1)); //True
		
	}

}