return new QueuingRemovalListener<>();
  }

  /** Type-inferring factory method for creating a {@link CountingRemovalListener}. */
  static <K, V> CountingRemovalListener<K, V> countingRemovalListener() {
    return new CountingRemovalListener<>();
  }

  /** {@link RemovalListener} that adds all {@link RemovalNotification} objects to a queue. */
  @GwtIncompatible // ConcurrentLinkedQueue