Why is synchronized block better than synchronized method?

Question

I have started learning synchronization in threading.

Synchronized method:

public class Counter {

   private static int count = 0;

   public stati         


        

Answer 1

Because lock is expensive, when you are using synchronized block you lock only if _instance == null, and after _instance finally initialized you'll never lock. But when you synchronize on method you lock unconditionally, even after the _instance is initialized. This is the idea behind double-checked locking optimization pattern http://en.wikipedia.org/wiki/Double-checked_locking.