SettableFuture<String> future2 = SettableFuture.create();
    ListenableFuture<List<String>> compound = allAsList(future1, future2);
    // There was a bug where the event listener for the combined future would
    // result in the sub-futures being cancelled without being interrupted.
    ListenableFuture<List<String>> otherCompound = allAsList(future1, future2);

    SettableFuture<String> future2 = SettableFuture.create();
    ListenableFuture<List<String>> compound = allAsList(future1, future2);
    // There was a bug where the event listener for the combined future would
    // result in the sub-futures being cancelled without being interrupted.
    ListenableFuture<List<String>> otherCompound = allAsList(future1, future2);

  /** How long after the last write an entry becomes a candidate for refresh. */
  final long refreshNanos;

  /** Entries waiting to be consumed by the removal listener. */
  // TODO(fry): define a new type which creates event objects and automates the clear logic
  final Queue<RemovalNotification<K, V>> removalNotificationQueue;

  /**
   * A listener that is invoked when an entry is removed due to expiration or garbage collection of