Program: How to create a TreeSet with comparator?

To implement your own sorting functionality with TreeSet, you have to pass Comparator object along with TreeSet constructor call. The Comparator implementation holds the sorting logic. You have to override compare() method to provide the sorting logic. Below example shows how to sort TreeSet using comparator.

package com.java2novice.treeset;

import java.util.Comparator;
import java.util.TreeSet;

public class MySetWithCompr {

	public static void main(String a[]){
		
		TreeSet<String> ts = new TreeSet<String>(new MyComp());
		ts.add("RED");
		ts.add("ORANGE");
		ts.add("BLUE");
		ts.add("GREEN");
		System.out.println(ts);
	}
}

class MyComp implements Comparator<String>{

	@Override
	public int compare(String str1, String str2) {
		return str1.compareTo(str2);
	}
	
}

[BLUE, GREEN, ORANGE, RED]