/**
     * A queue of elements currently in the map, ordered by write time. Elements are added to the
     * tail of the queue on write.
     */
    @GuardedBy("this")
    final Queue<ReferenceEntry<K, V>> writeQueue;

    /**
     * A queue of elements currently in the map, ordered by access time. Elements are added to the
     * tail of the queue on access (note that writes count as accesses).

   * formally, removes an element {@code e} such that {@code o.equals(e)}, if this queue contains
   * one or more such elements. Returns {@code true} if and only if this queue contained the
   * specified element (or equivalently, if this queue changed as a result of the call).
   *
   * @param o element to be removed from this queue, if present

/**
 * A bounded {@linkplain BlockingQueue blocking queue} backed by an array. This queue orders
 * elements FIFO (first-in-first-out). The head of the queue is that element that has been
 * on the queue the longest time. The tail of the queue is that element that has been on
 * the queue the shortest time. New elements are inserted at the tail of the queue, and the queue
 * retrieval operations obtain elements at the head of the queue.

   * getting a bunch of different keys), then makes sure all the items in the cache are also in the
   * eviction queue. It will invoke the given {@code operation} on the first element in the eviction
   * queue, and then reverify that all items in the cache are in the eviction queue, and verify that
   * the head of the eviction queue has changed as a result of the operation.
   */
  static void checkRecency(

import java.util.Collection;
import java.util.Queue;

/**
 * A non-blocking queue which automatically evicts elements from the head of the queue when
 * attempting to add new elements onto the queue and it is full. This queue orders elements FIFO
 * (first-in-first-out). This data structure is logically equivalent to a circular buffer (i.e.,
 * cyclic buffer or ring buffer).
 *

 */
public final class Crawler {
  private final OkHttpClient client;
  private final Set<HttpUrl> fetchedUrls = Collections.synchronizedSet(new LinkedHashSet<>());
  private final LinkedBlockingQueue<HttpUrl> queue = new LinkedBlockingQueue<>();
  private final ConcurrentHashMap<String, AtomicInteger> hostnames = new ConcurrentHashMap<>();

  public Crawler(OkHttpClient client) {
    this.client = client;
  }

    private final BlockingQueue<String> queue;

    public EnableWrites(BlockingQueue<String> queue, long tMinus) {
      super(tMinus);
      assertFalse(queue.isEmpty());
      assertFalse(queue.offer("shouldBeRejected"));
      this.queue = queue;
    }

    @Override
    protected void doAction() {
      assertNotNull(queue.remove());
    }
  }

  private final Queue<T> queue;

  ConsumingQueueIterator(Queue<T> queue) {
    this.queue = checkNotNull(queue);
  }

  @Override
  @CheckForNull
  protected T computeNext() {
    // TODO(b/192579700): Use a ternary once it no longer confuses our nullness checker.
    if (queue.isEmpty()) {
      return endOfData();
    }
    return queue.remove();
  }

  }

  private void enqueueHelper(Event<L> event, Object label) {
    checkNotNull(event, "event");
    checkNotNull(label, "label");
    synchronized (listeners) {
      for (PerListenerQueue<L> queue : listeners) {
        queue.add(event, label);
      }
    }
  }

  /**
   * Dispatches all events enqueued prior to this call, serially and in order, for every listener.
   *

	if !utf8.Valid(next) {
		return errInvalidTextEncodingError()
	}

	// Create queue
	r.queue = make(chan *queueItem, runtime.GOMAXPROCS(0))
	r.input = make(chan *queueItem, runtime.GOMAXPROCS(0))
	r.readerWg.Add(1)

	// Start splitter
	go func() {
		defer close(r.input)
		defer close(r.queue)
		defer r.readerWg.Done()
		for {
			q := queueItem{
				input: next,