Re: problem with Sets

"bassel" <>
21 Sep 2006 03:57:39 -0700

TreeSet instance performs all key comparisons using its compareTo (or
compare) method, so two keys that are deemed equal by this method are,
from the standpoint of the set, equal. The behavior of a set is
well-defined even if its ordering is inconsistent with equals; it just
fails to obey the general contract of the Set interface."

it's clear now, TreeSet deals with only compareTo and my class was like

package test;

 * @author Administrator
public class Identity implements Comparable{

    private String name;
    private long id;

    public void setName(String name){ = name;
    public void setId(long id){ = id;

    public String getName(){
    public double getId(){

    public boolean equals(Object obj){
        System.out.println("equals says: I'm invoked");
            Identity otherIdentity = (Identity)obj;
            return (;
        }catch(ClassCastException e){
            return false;

    public int compareTo(Object obj){
        System.out.println("compareTo says: I'm invoked");
        Identity otherIdentity = (Identity)obj;
        if ( > otherIdentity.getId())
            return 1;
        else if ( < otherIdentity.getId())
            return -1;
            return 0;

    public int hashCode(){
        return name.hashCode();

so the compareTo() was not consistent with equals().

thank you,


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