code: void unregisterOutputStream(OutStream stream) {
  		lock.lock();
  		try {
  			// only decrement if we actually remove the stream
  			if (openOutputStreams.remove(stream)) {
  				numReservedOutputStreams--;
  				available.signalAll();
  			}
  		}
  		finally {
  			lock.unlock();
  		}
  	}
docs: Atomically removes the given output stream from the set of currently open output streams,
  and signals that new stream can now be opened.