@Override
  @CheckForNull
  public Entry<K, V> firstEntry() {
    return Iterators.<@Nullable Entry<K, V>>getNext(entryIterator(), null);
  }

  @Override
  @CheckForNull
  public Entry<K, V> lastEntry() {
    return Iterators.<@Nullable Entry<K, V>>getNext(descendingEntryIterator(), null);
  }

  @Override
  @CheckForNull
  public Entry<K, V> pollFirstEntry() {

      assertEquals(hashOne, entryOne.getHash());
      assertNull(entryOne.getNext());
      assertSame(valueOne, copyOne.getValue());

      InternalEntry<Object, Object, ?> copyTwo = segment.copyForTesting(entryTwo, copyOne);
      assertSame(keyTwo, copyTwo.getKey());
      assertEquals(hashTwo, copyTwo.getHash());
      assertSame(copyOne, copyTwo.getNext());
      assertSame(valueTwo, copyTwo.getValue());
    }
  }

      assertEquals(hashOne, entryOne.getHash());
      assertNull(entryOne.getNext());
      assertSame(valueOne, copyOne.getValue());

      InternalEntry<Object, Object, ?> copyTwo = segment.copyForTesting(entryTwo, copyOne);
      assertSame(keyTwo, copyTwo.getKey());
      assertEquals(hashTwo, copyTwo.getHash());
      assertSame(copyOne, copyTwo.getNext());
      assertSame(valueTwo, copyTwo.getValue());
    }
  }

    Iterator<String> iterator = Collections.singletonList("foo").iterator();
    assertEquals("foo", Iterators.getNext(iterator, "bar"));
  }

  public void testGetNext_withDefault_empty() {
    Iterator<String> iterator = Iterators.emptyIterator();
    assertEquals("bar", Iterators.getNext(iterator, "bar"));
  }

  public void testGetNext_withDefault_empty_null() {

      Iterators.advance(iterator, position);
      return Iterators.getNext(iterator, defaultValue);
    }
  }

  /**
   * Returns the first element in {@code iterable} or {@code defaultValue} if the iterable is empty.
   * The {@link Iterators} analog to this method is {@link Iterators#getNext}.
   *
   * <p>If no default value is desired (and the caller instead wants a {@link

  @GwtIncompatible // NavigableSet
  @Override
  @CheckForNull
  public E lower(E e) {
    return Iterators.<@Nullable E>getNext(headSet(e, false).descendingIterator(), null);
  }

  /** @since 12.0 */
  @Override
  @CheckForNull
  public E floor(E e) {
    return Iterators.<@Nullable E>getNext(headSet(e, true).descendingIterator(), null);
  }

  /** @since 12.0 */
  @Override
  @CheckForNull

  @Override
  @CheckForNull
  public Entry<K, V> firstEntry() {
    return Iterators.<@Nullable Entry<K, V>>getNext(entryIterator(), null);
  }

  @Override
  @CheckForNull
  public Entry<K, V> lastEntry() {
    return Iterators.<@Nullable Entry<K, V>>getNext(descendingEntryIterator(), null);
  }

  @Override
  @CheckForNull
  public Entry<K, V> pollFirstEntry() {

    ReferenceEntry<K, V> removeEntryFromChain(
        ReferenceEntry<K, V> first, ReferenceEntry<K, V> entry) {
      int newCount = count;
      ReferenceEntry<K, V> newFirst = entry.getNext();
      for (ReferenceEntry<K, V> e = first; e != entry; e = e.getNext()) {
        ReferenceEntry<K, V> next = copyEntry(e, newFirst);
        if (next != null) {
          newFirst = next;
        } else {
          removeCollectedEntry(e);

      assertNull(entryOne.getNext());
      assertSame(valueOne, copyOne.getValueReference().get());
      assertConnected(map, copyOne, entryTwo);

      ReferenceEntry<Object, Object> copyTwo = map.copyEntry(entryTwo, copyOne);
      assertSame(keyTwo, copyTwo.getKey());
      assertEquals(hashTwo, copyTwo.getHash());
      assertSame(copyOne, copyTwo.getNext());

      assertNull(entryOne.getNext());
      assertSame(valueOne, copyOne.getValueReference().get());
      assertConnected(map, copyOne, entryTwo);

      ReferenceEntry<Object, Object> copyTwo = map.copyEntry(entryTwo, copyOne);
      assertSame(keyTwo, copyTwo.getKey());
      assertEquals(hashTwo, copyTwo.getHash());
      assertSame(copyOne, copyTwo.getNext());