* stack so that it is returned by the next call to {@link Iterator#next()}. If the element is
     * not in {@link #nextElements}, this method throws an {@link UnknownElementException}.
     *
     * <p>This method is used when testing iterators without a known ordering. We poll the target
     * iterator's next element and pass it to the reference iterator through this method so it can

    }

    /**
     * Checks if there is a next page available.
     *
     * @return true if there is a next page, false otherwise
     */
    public boolean isExistNextPage() {
        return existNextPage;
    }

    /**
     * Sets whether there is a next page available.
     *
     * @param existNextPage true if there is a next page, false otherwise
     */

        // Act & Assert: entries a, b, c (dot entries filtered) then end
        assertTrue(it.hasNext());
        assertEquals("a", it.next().getName());
        assertTrue(it.hasNext());
        assertEquals("b", it.next().getName());
        assertTrue(it.hasNext());
        assertEquals("c", it.next().getName());
        assertFalse(it.hasNext());

        // Verify interactions

   * remain. This method is invoked during each call to {@link #next()} in order to compute the
   * result of a <i>future</i> call to {@code next()}.
   */
  protected abstract @Nullable T computeNext(T previous);

  @Override
  public final boolean hasNext() {
    return nextOrNull != null;
  }

  @Override
  public final T next() {
    if (nextOrNull == null) {
      throw new NoSuchElementException();

                    // move on to next in r1
                    if (i1.hasNext()) {
                        res1 = i1.next();
                    } else {
                        done = true;
                    }
                }
            } else {
                // move on to next in r2
                if (i2.hasNext()) {
                    res2 = i2.next();
                } else {

   * remain. This method is invoked during each call to {@link #next()} in order to compute the
   * result of a <i>future</i> call to {@code next()}.
   */
  protected abstract @Nullable T computeNext(T previous);

  @Override
  public final boolean hasNext() {
    return nextOrNull != null;
  }

  @Override
  public final T next() {
    if (nextOrNull == null) {
      throw new NoSuchElementException();

    }

    return b1;
  }

  /**
   * Reads an unsigned {@code short} as specified by {@link DataInputStream#readUnsignedShort()},
   * except using little-endian byte order.
   *
   * @return the next two bytes of the input stream, interpreted as an unsigned 16-bit integer in
   *     little-endian byte order
   * @throws IOException if an I/O error occurs
   */
  @CanIgnoreReturnValue // to skip some bytes
  @Override

                return Integer.valueOf(from);
              }
            });

    Iterator<Integer> resultIterator = result.iterator();
    resultIterator.next();

    assertThrows(NumberFormatException.class, () -> resultIterator.next());
  }

  public void testNullFriendlyTransform() {
    List<@Nullable Integer> input = asList(1, 2, null, 3);
    Iterable<String> result =
        Iterables.transform(

    }

    /**
     * Checks if a next page exists.
     *
     * @return true if a next page exists, false otherwise
     */
    public boolean isExistNextPage() {
        return existNextPage;
    }

    /**
     * Sets whether a next page exists.
     *
     * @param existNextPage true if a next page exists, false otherwise
     */

   */
  public abstract @Nullable C previous(C value);

  /**
   * Returns a signed value indicating how many nested invocations of {@link #next} (if positive) or
   * {@link #previous} (if negative) are needed to reach {@code end} starting from {@code start}.
   * For example, if {@code end = next(next(next(start)))}, then {@code distance(start, end) == 3}
   * and {@code distance(end, start) == -3}. As well, {@code distance(a, a)} is always zero.
   *