catch(QueueClosedException closed) {
catch(QueueClosedException closed_ex) {
    public void close(boolean flush_entries) {        if(flush_entries) {            try {                add(endMarker); // add an end-of-entries marker to the end of the queue                num_markers++;            }            catch(QueueClosedException closed) {            }            return;        }        synchronized(mutex) {            closed=true;            mutex.notifyAll();        }//        synchronized(remove_mutex) {//            remove_mutex.notifyAll();//        }    }