java design patterns

1// double locking is used to reduce the overhead of the synchronized method
2public static ThreadSafeSingleton getInstanceDoubleLocking() {
3	if (instance == null) {
4		synchronized (ThreadSafeSingleton.class) {
5			if (instance == null) {
6				instance = new ThreadSafeSingleton();
7			}
8		}
9	}
10	return instance;
11}