Duplicate elements - TreeSet

Question

I've got the following user-defined class:
class User{
     public String name = null;
     public String add = null;
     public String getName(){     
          return name;
     public String getAdd(){
          return add;
     public void setName(String name){
          this.name = name;
     public void setAdd(String add){
          this.add = add;
public static void main(String args[]){
          User u1 = new User();
          User u2 = new User();
          u1.setName("A");
          u2.setName("A");
          u1.setAdd("A");
          u2.setAdd("B");
          TreeSet ts = new TreeSet();
          System.out.println(ts.add(u1));
// This line throws classcastexception
          System.out.println(ts.add(u2));
I need to add the objects of this class in a set so the duplicate objects are eliminated. The above code when run throws classcastexception.
Is there any workaround.Pls help me.
Thanks.

Answer 1

In addition to what the others have said, I would suggest overriding equals and hashCode. I don't think it's strictly necessary for putting things in a TreeSet, but it's probably a good idea, especially if you go the Coparable router (as opposed to Comparator).
Here's some stuff you may find useful:
Making Java Objects Comparable
http://java.sun.com/docs/books/tutorial/collections/interfaces/order.html
http://www.javaworld.com/javaworld/jw-12-2002/jw-1227-sort.html
http://developer.java.sun.com/developer/Books/effectivejava/Chapter3.pdf