Question

class A {     public synchronized void myOneMethod() {         // ...     } }  class B extends A {     public synchronized void myOtherMethod() {         // ...     } }  // ...  B myObject;  // ...  myObject.myOneMethod(); // acquires lock myObject.myOtherMethod(); // same lock? 

How I understand the synchronization model, I’d say that yes, it does, because the lock / monitor is associated with the instance myObject, and it doesn’t matter where the method was defined. But am I right? If not, why? If yes, why are you sure, and I’m not? 🙂

Answer 1

Yes, you are right, and you got the explanation right too. Nothing much to add.

Note that if the methods were static, then they would synchronize on different objects, namely their respective classes (A and B).

EDIT: Why am I sure? I don’t know, why are you not sure? 😉 myObject is just one object – there isn’t any distinction between the myObject attributes that come from class A and those that come from class B. (Well, technically you could probably use reflection to find out which are which, so there must be some distinction, but forget about reflection for now. For common operations on the object there’s no distinction.)