Singleton - Multiple Users [Thread Safe]

Following is the way by which we can use Singleton Design pattern for multiple users.

public class Singleton {
         private volatile static Singleton singleton; //volatile is needed so that multiple thread can reconcile the instance
         private Singleton(){
         }

         public static Singleton getSingleton(){ //synchronized keyword has been removed from here
         if(singleton = = null)
         {          //needed because once there is singleton available no need to aquire monitor again & again as it is costly
                synchronized(Singleton.class)
                {
                        //this is needed if two threads are waiting at the monitor at the time when singleton was getting instantiated
                      if(singleton==null)
                      {      
                              singleton= new Singleton();
                       }
                  }
          }
          return singleton;
    }
}