Note to self. synchronized singleton access

So, what's the best thread safe singleton instantiation.. I must look this up sometime.

Here's what we have now.

public static SingletonObject getInstance() {
 if (instance == null) {
  synchronized (SingletonObject.class) {
                        // might have been preempted just after first check 
                        // but before the synchronized statement was executed
   if (instance == null) {
    instance = new SingletonObject();
   }
  }
 }
 return instance;
}