else {
        nextIndex = takeIndex;
        nextItem = items[takeIndex];
      }
    }

    @Override
    public boolean hasNext() {
      /*
       * No sync. We can return true by mistake here
       * only if this iterator passed across threads,
       * which we don't support anyway.
       */
      return nextIndex >= 0;
    }

    /**

   * the warnings the {@link MoreExecutors#directExecutor} documentation.
   *
   * <p>The returned {@code Future} attempts to keep its cancellation state in sync with that of the
   * input future and that of the future returned by the chain function. That is, if the returned
   * {@code Future} is cancelled, it will attempt to cancel the other two, and if either of the