BlockingQueue<T> q,
      Collection<? super T> buffer,
      int maxElements,
      long timeout,
      TimeUnit unit,
      boolean interruptibly)
      throws InterruptedException {
    return interruptibly
        ? Queues.drain(q, buffer, maxElements, timeout, unit)
        : Queues.drainUninterruptibly(q, buffer, maxElements, timeout, unit);
  }

  public void testMultipleProducers() throws Exception {

  @Override
  public int drainTo(Collection<? super E> c, int maxElements) {
    if (c == null) throw new NullPointerException();
    if (c == this) throw new IllegalArgumentException();
    if (maxElements <= 0) return 0;
    final Monitor monitor = this.monitor;
    monitor.enter();
    try {
      int n = 0;
      E e;
      while (n < maxElements && (e = q.poll()) != null) {
        c.add(e);
        ++n;