Serializable Singleton Program in Java

import java.io.*;

public class SerializableSingleton implements java.io.Serializable
 {
       static SerializableSingleton singleton;
   protected SerializableSingleton()
    {
      // Exists only to thwart instantiation.
    }
      private Object readResolve()
    {
           return instancd;
    }
    public static void main(String args[])
        {
            singleton = new SerializableSingleton();
            singleton.readResolve();
        }
}