public static MySingleton getInstance() {
 if (_instance==null) {
   synchronized (MySingleton.class) {
      _instance = new MySingleton();
   }
 }
 return _instance;
} 

1.is there a flaw with the above implementation of the getInstance method? 2.What is the difference between the two implementations.?

public static synchronized MySingleton getInstance() { 
 if (_instance==null) {
  _instance = new MySingleton();
 }

 return _instance;
} 

I have seen a lot of answers on the singleton pattern in stackoverflow but the question I have posted is to know mainly difference of 'synchronize' at method and block level in this particular case.