Do synchronized methods have locks of their own?

Question

Suppose I have

class myClass {

    synchronized methodA { };

    synchronized methodB { };
}

Does it mean that there are 2 implicit locks? One for methodA and one for B? I was reading Cracking the Coding Interview by Gayle McDowell, and she says that locking happens at the level of method + object, as opposed to object. I was under the impression that myClass simply has one lock and every synchronized method uses that. Can anyone explain ?

Answer 1

This

synchronized void methodA 
{
  //code
}

is equivalent to

void methodA 
{
  synchronized(this)
  {
    //code
  }

}

So, synchronized in front of a method will use the instance of the object itself as a lock.

Answer 2

Both of this methods used same lock. Every object in java has his internal mutex.

synchronized void method() {}

and

synchronized(this) {}

used same lock.

But if you try synchronized on static method - it will use different locks:

static synchronized method() { // used Class lock ! not object lock
}