Program: How to avoid duplicate user defined objects in TreeSet?

To avoid duplicate user defined objects in TreeSet, you have to implement Comparator interface with equality verification. Below example gives a sample code to implement it.

package com.java2novice.treeset;

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

public class MyUserDuplicates {

	public static void main(String a[]){
		
		Set<Emp> ts = new TreeSet<Emp>(new EmpComp());
		ts.add(new Emp(201,"John",40000));
		ts.add(new Emp(302,"Krish",44500));
		ts.add(new Emp(146,"Tom",20000));
		ts.add(new Emp(543,"Abdul",10000));
		ts.add(new Emp(12,"Dinesh",50000));
		//adding duplicate entry
		ts.add(new Emp(146,"Tom",20000));
		//check duplicate entry is there or not
		for(Emp e:ts){
			System.out.println(e);
		}
	}
}

class EmpComp implements Comparator<Emp>{

	@Override
	public int compare(Emp e1, Emp e2) {
		if(e1.getEmpId() == e2.getEmpId()){
			return 0;
		} if(e1.getEmpId() < e2.getEmpId()){
			return 1;
		} else {
			return -1;
		}
	}
}

class Emp {
	
	private int empId;
	private String empName;
	private int empSal;
	
	public Emp(int id, String name, int sal){
		this.empId = id;
		this.empName = name;
		this.empSal = sal;
	}
	
	public int getEmpId() {
		return empId;
	}
	
	public void setEmpId(int empId) {
		this.empId = empId;
	}
	
	public String getEmpName() {
		return empName;
	}
	
	public void setEmpName(String empName) {
		this.empName = empName;
	}
	
	public int getEmpSal() {
		return empSal;
	}
	public void setEmpSal(int empSal) {
		this.empSal = empSal;
	}
	
	public String toString(){
		return empId+" : "+empName+" : "+empSal;
	}
}

543 : Abdul : 10000
302 : Krish : 44500
201 : John : 40000
146 : Tom : 20000
12 : Dinesh : 50000