// 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

      }

      @Override
      @ParametricNullness
      public E next() {
        Map.Entry<E, Count> mapEntry = backingEntries.next();
        toRemove = mapEntry;
        return mapEntry.getKey();
      }

      @Override
      public void remove() {
        checkState(toRemove != null, "no calls to next() since the last call to remove()");
        size -= toRemove.getValue().getAndSet(0);

        assertSame(fe1, it.next(), "First element must match first page");
        assertTrue(it.hasNext(), "Iterator should have second element");
        assertSame(fe2, it.next(), "Second element must match first page");

        // Next page fetched via fetchMore()
        assertTrue(it.hasNext(), "Iterator should have third element after fetchMore");
        assertSame(fe3, it.next(), "Third element from second page");

     * 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

     */
    boolean isIntermediate();

    /**
     * Combine this referral with another to form a chain
     *
     * @param next the referral to combine with
     * @return new referral, combining a chain of referrals
     */
    DfsReferralDataInternal combine(DfsReferralData next);

    /**
     * Append another referral to this referral chain
     *
     * @param dr the referral to append
     */

    assertEquals(immutableEntry("foo", 5), entryIterator.next());
    assertEquals(immutableEntry("bar", 4), entryIterator.next());
    assertEquals(immutableEntry("foo", 3), entryIterator.next());
    assertEquals(immutableEntry("cow", 2), entryIterator.next());
    assertEquals(immutableEntry("bar", 1), entryIterator.next());

    Iterator<Entry<String, Collection<Integer>>> collectionIterator =

    Iterator<String> keyIterator = keys.iterator();
    keyIterator.next();
    keyIterator.remove();
    assertFalse(underlying.containsKey("c"));

    Collection<String> values = map.values();
    values.remove("4");
    assertFalse(underlying.containsKey("d"));

    Iterator<String> valueIterator = values.iterator();
    valueIterator.next();
    valueIterator.remove();
    assertFalse(underlying.containsKey("e"));

   * 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();

    }

    /**
     * Returns true if a next page exists.
     *
     * @return True if a next page exists.
     */
    public boolean isExistNextPage() {
        return existNextPage;
    }

    /**
     * Sets whether a next page exists.
     *
     * @param existNextPage True if a next page exists.
     */
    public void setExistNextPage(final boolean existNextPage) {

                        public boolean hasNext() {
                            return false;
                        }

                        @Override
                        public Entry<Object, Object> next() {
                            throw new NoSuchElementException();
                        }
                    };
                }

                @Override
                public int size() {