SASL Authentication Failure (DIGEST-MD5) Using SMACK

Question

Possible duplicate:
SASL authentication error while integrating facebook chat using Smack

I am trying to compile this code and always throw this exception

SASL authentication error using the DIGEST-MD5 mechanism:
    on org.jivesoftware.smack.SASLAuthentication.authenticate (SASLAuthentication.java:325)
    on org.jivesoftware.smack.XMPPConnection.login (XMPPConnection.javahaps95)
    on org.jivesoftware.smack .XMPPConnection.login (XMPPConnection.javahaps49)
    at SimpleConnection.main (SimpleConnection.java:31)

The code:

import javax.swing.JOptionPane;
import org.jivesoftware.smack.Chat;
import org.jivesoftware.smack.XMPPConnection;

import org.jivesoftware.smack.ConnectionConfiguration;
import org.jivesoftware.smack.MessageListener;

import org.jivesoftware.smack.SASLAuthentication;

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */

public class SimpleConnection {

    static String username = "";
    static String password = "";

    public SimpleConnection() {
    }

    public static void main(String[] args) {
        try {

           SASLAuthentication.registerSASLMechanism("DIGEST-MD5", MySASLDigestMD5Mechanism.class);
            ConnectionConfiguration conf = new ConnectionConfiguration("chat.facebook.com", 5222);
            XMPPConnection con = new XMPPConnection(conf);
            con.connect();
            con.login(username, password);

            //Chat c = con.getChatManager().createChat("atopmax", new aa());
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

What am I doing wrong? Thank!