Explicit unlimited counting semaphore?

I need to provide a method that blocks until all outstanding work in BlockingQueue is processed.

I thought I could handle this by counting a semaphore that starts at 0 and decreases as items are added to the queue and increase as they complete. finish () just acquired a semaphore, let it go and left.

Perhaps I could call reducePermits (). Does this work if the number of permissions is already <0? It is protected, so I need to extend the Semaphore class to make it work.

My second best idea is to check the contents of the queue in a loop and sleep for 100 ms between checks. It works, but it seems kludgey.

TIA - Tim.

public MyClass {
  public class MySemaphore extends Semaphore {
    public void seize() {
      reducePermits(1);
    }
  }
  private MySemaphore allDone = new MySemaphore();
  void startSomething() {
    allDone.seize();
  }
  void finishSomething() {
    allDone.release();
  }
  void finish() {
    allDone.acquire();
    allDone.release();
  }
}