Java: Is volatile / final required for reference to synchronized object?

Question

This seems a pretty basic issue, but I cannot find a clear confirmation.

Let\'s say I have a class properly synchronized in itself:

public class Sync         


        

Answer 1

If I need to have a refence to an instance of that class, shared between threads, I do still need to declare that instance volatile or final, am I right?

Yes, you are right. In this case you have two shared variables:

private int field

private SyncClass mySharedObject

Because of the way you have defined SyncClass any reference to a SyncClass will give you the most up to date value of that SyncClass.

If you don't synchronize the access to mySharedObject correctly (a non-final, non-volatile) field and you change the value of mySharedObject you may get a mySharedObject which is out of date.