Hi all, I was reading this article about "Double-Checked locking" and out of the main topic of the article I was wondering why at some point of the article the author uses the next Idiom:
Listing 7. Attempting to solve the out-of-order write problem
public static Singleton getInstance() { if (instance == null) { synchronized(Singleton.class) { //1 Singleton inst = instance; //2 if (inst == null) { synchronized(Singleton.class) { //3 inst = new Singleton(); //4 } instance = inst; //5 } } } return instance; }
And my question is: Is there any reason to syncronize twice some code with the same lock? Have this any purpose it?
Many thanks in advance.