Java's Comparable Interface

When calling Collections.sort(), compareTo() is implicitly called as well. To override compareTo(), do the following:

@Override
public int compareTo(<Object> o){
	if(this.var > o.getVar()){
		return 1;
	} else if(this.var < o.getVar()) {
		return -1;
	} else {
		return 0;
	}
}

The values 1, -1, and 0, are all used by the Collections.sort() method to determine where to put elements of an ArrayList.

x	y	z	x’y’z’	output
0	0	0	1	1