Two questions regarding synchronization
Should synchronized object be the same as the object of the wait method ? Can I do like this :
synchronized (o) { try { this.wait(); } catch (InterruptedException e) { } } An IllegalThreadStateException is thrown if the current thread fails to synchronize on an object before calling its wait() or notify() methods. So, no, it isn't useful.
Yes, to reiterate the above, the thread must synchronize on the same instance upon which it invokes wait() or notify(). So the example will only work if o == this.
I don't find good reasons to use wait() and notify() since java.util.concurrent was introduced, and synchronized is less useful now too. I recommend the higher-level tools in that package to both beginners (as easier to use) and advanced (more powerful and correct) programmers.
1. You can't call wait() or notify()/notifyAll() outside of synchronized blocks that synchronize on the the object the method calls belong to. If you try, you'll get an IllegalMonitorStateException.
2. You are required to synchronize on the same object that your wait()/notify()/notifyAll() calls belong to. For instance, your code will throw an IMSE as written. You'll want to call synchronized(this){ ... instead.
