Implementation of a multithreaded singleton in Java

package yn.graph;

/**
 * @author ny
 * 
 */
public class MultithreadedSingleton {
 private static final MultithreadedSingleton singleton = new MultithreadedSingleton();
 
 private MultithreadedSingleton() {
  synchronized (MultithreadedSingleton.class) {
   //initialize the variables   
  }
 }

 public static MultithreadedSingleton getSingleton() {
  return singleton;
 }

 private static class TestMultithreadedSingleton implements Runnable {
  @Override
  public void run() {
   MultithreadedSingleton sgt = getSingleton();
   System.out.println(sgt);
  }
 }
 
 /**
  * @param args
  */
 public static void main(String[] args) {
  new Thread(new TestMultithreadedSingleton()).start();
  new Thread(new TestMultithreadedSingleton()).start();
  new Thread(new TestMultithreadedSingleton()).start();
  new Thread(new TestMultithreadedSingleton()).start();
  new Thread(new TestMultithreadedSingleton()).start();
 }
}