FAILED,
  }

  @CheckForNull private T next;

  /**
   * Returns the next element. <b>Note:</b> the implementation must call {@link #endOfData()} when
   * there are no elements left in the iteration. Failure to do so could result in an infinite loop.
   *
   * <p>The initial invocation of {@link #hasNext()} or {@link #next()} calls this method, as does

    FAILED,
  }

  @CheckForNull private T next;

  /**
   * Returns the next element. <b>Note:</b> the implementation must call {@link #endOfData()} when
   * there are no elements left in the iteration. Failure to do so could result in an infinite loop.
   *
   * <p>The initial invocation of {@link #hasNext()} or {@link #next()} calls this method, as does