Exception null pointer Exception

Bonjour,
jai cette erreur lors de l'exécution de ce code:

java.lang.NullPointerException
at weapplication1.Administrateur.authentifier(Administrateur.java:42)
at weapplication1.Administrateur.main(Administrateur.java:54)
BUILD SUCCESSFUL (total time: 1 second)

/*
* Administrateur.java
*
* Created on 2 mai 2008, 22:13
*
* To change this template, choose Tools | Template Manager
* and open the template in the editor.
*/

package weapplication1;

/**
*
* @author Administrateur
*/
import java.sql.*;
import java.io.*;
import java.util.*;

public class Administrateur {
public Connection c;
public Statement stmt;
public ResultSet rs,rs1;
public String query ;
String login;
String mpd;
public Administrateur(String login,String mpd)
{this.login=login;
this.mpd=mpd;
}
/** Creates a new instance of Administrateur */
public Administrateur()throws ClassNotFoundException, SQLException {

Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");

Connection con = DriverManager.getConnection("jdbc:odbc:Super");
}
public void authentifier(String login,String mot_de_passe) throws ClassNotFoundException,SQLException
{
query= "SELECT * from administrateur where login='"+login+"' and mpd='"+mot_de_passe+"'";

rs=stmt.executeQuery(query);
if(rs.next()){
System.out.println(rs.getString(1) + rs.getString(2));

}

}
public static void main(String args[])
{
try
{Administrateur a=new Administrateur();
a.authentifier("admin","admin");
}
catch(SQLException sqle){System.err.println(sqle.getStackTrace());}
catch(ClassNotFoundException cnfe){System.err.println("Probleme authentification");}
catch(Exception e){e.printStackTrace();}

}
}