Iterator<Entry<E>> entryIterator = entryIterator();
    return entryIterator.hasNext() ? entryIterator.next() : null;
  }

  @Override
  public @Nullable Entry<E> lastEntry() {
    Iterator<Entry<E>> entryIterator = descendingEntryIterator();
    return entryIterator.hasNext() ? entryIterator.next() : null;
  }

  @Override
  public @Nullable Entry<E> pollFirstEntry() {

        this.existPrePage = existPrePage;
    }

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

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

    assertEquals(
        "multiset.entrySet() iterator.next() returned incorrect entry",
        Multisets.immutableEntry(e0(), 1),
        iterator.next());
    assertFalse(
        "size 1 multiset.entrySet() iterator.hasNext() returned true after next()",
        iterator.hasNext());
    iterator.remove();
    assertTrue(

    }

    @Test
    @DisplayName("Should get next referral")
    void testNext() {
        // Given
        DfsReferralData nextReferral = mock(DfsReferralData.class);
        when(mockReferralData.next()).thenReturn(nextReferral);

        // When
        DfsReferralData result = mockReferralData.next();

        // Then
        assertEquals(nextReferral, result);

    assertEquals(
        "next() should still return first element after peeking", "A", peekingIterator.next());

    assertEquals("Should be able to peek() at middle element", "B", peekingIterator.peek());
    assertEquals(
        "Should be able to peek() middle element multiple times", "B", peekingIterator.peek());
    assertEquals(

   * part of the smeared hash of the key not covered by the hashtable mask, whereas the low bits are
   * the "next" pointer (pointing to the next entry in the bucket chain), which will always be less
   * than or equal to the hashtable mask.
   *
   * <pre>
   * hash  = aaaaaaaa
   * mask  = 00000fff
   * next  = 00000bbb
   * entry = aaaaabbb
   * </pre>
   *

        final LineIterator it = new LineIterator(reader);
        assertThat(it.hasNext(), is(true));
        assertThat(it.next(), is("aaa"));
        assertThat(it.hasNext(), is(true));
        assertThat(it.next(), is("bbb"));
        assertThat(it.hasNext(), is(true));
        assertThat(it.next(), is("ccc"));
        assertThat(it.hasNext(), is(not(true)));
    }

    /**
     * @throws Exception
     */
    @Test

    checkNotNull(comparator);
    Iterator<? extends T> it = iterable.iterator();
    if (it.hasNext()) {
      T prev = it.next();
      while (it.hasNext()) {
        T next = it.next();
        if (comparator.compare(prev, next) > 0) {
          return false;
        }
        prev = next;
      }
    }
    return true;
  }

  /**

  private int position;

  /** Returns the element with the specified index. This method is called by {@link #next()}. */
  @ParametricNullness
  protected abstract E get(int index);

  /**
   * Constructs an iterator across a sequence of the given size whose initial position is 0. That
   * is, the first call to {@link #next()} will return the first element (or throw {@link
   * NoSuchElementException} if {@code size} is zero).
   *

    @Override
    public DfsReferralDataImpl next() {
        return this.next;
    }

    /**
     * Append another referral to this referral chain
     *
     * @param dr the referral to append
     */
    @Override
    public void append(final DfsReferralDataInternal dr) {
        final DfsReferralDataImpl dri = (DfsReferralDataImpl) dr;
        dri.next = this.next;
        this.next = dri;
    }