Missing volatile keyword

[vskishan]

From the class ThreadSafeSingleton.java at path design-patterns/java/singleton/ThreadSafeSingleton.java

I could see that the below statement is missing the volatile keyword.

private static ThreadSafeSingleton instance;

Although we are breaking the contention using synchronized method, ongoing threads that try to access this method might still see that instance == null even after it has been instantiated.

CC : @ashishps1