verifySetContents(set, EMPTY_COLLECTION);
  }

  public void testNewLinkedHashSetWithExpectedSizeLarge() {
    LinkedHashSet<Integer> set = Sets.newLinkedHashSetWithExpectedSize(1000);
    verifySetContents(set, EMPTY_COLLECTION);
  }

  public void testNewTreeSetEmpty() {
    TreeSet<Integer> set = Sets.newTreeSet();
    verifySortedSetContents(set, EMPTY_COLLECTION, null);
  }

    SortedMapDifference<Integer, Integer> diff = Maps.difference(SORTED_EMPTY, SORTED_EMPTY);
    assertTrue(diff.areEqual());
    assertEquals(SORTED_EMPTY, diff.entriesOnlyOnLeft());
    assertEquals(SORTED_EMPTY, diff.entriesOnlyOnRight());
    assertEquals(SORTED_EMPTY, diff.entriesInCommon());
    assertEquals(SORTED_EMPTY, diff.entriesDiffering());
    assertEquals("equal", diff.toString());
  }

    SortedMapDifference<Integer, Integer> diff = Maps.difference(SORTED_EMPTY, SORTED_EMPTY);
    assertTrue(diff.areEqual());
    assertEquals(SORTED_EMPTY, diff.entriesOnlyOnLeft());
    assertEquals(SORTED_EMPTY, diff.entriesOnlyOnRight());
    assertEquals(SORTED_EMPTY, diff.entriesInCommon());
    assertEquals(SORTED_EMPTY, diff.entriesDiffering());
    assertEquals("equal", diff.toString());
  }

    assertEquals("foo", Iterators.getOnlyElement(iterator, "bar"));
  }

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

  public void testGetOnlyElement_withDefault_empty_null() {
    Iterator<String> iterator = Iterators.emptyIterator();

   *     // operate on tuple
   *   }
   * }
   * }</pre>
   *
   * <p>Note that if any input set is empty, the Cartesian product will also be empty. If no sets at
   * all are provided (an empty list), the resulting Cartesian product has one element, an empty
   * list (counter-intuitive, but mathematically consistent).
   *

   * uses less memory than TreeMap; then say so in the class Javadoc.
   */
  private static final Comparator<?> NATURAL_ORDER = Ordering.natural();

  private static final ImmutableSortedMap<Comparable<?>, Object> NATURAL_EMPTY_MAP =
      new ImmutableSortedMap<>(
          ImmutableSortedSet.emptySet(Ordering.natural()), ImmutableList.<Object>of());

  static <K, V> ImmutableSortedMap<K, V> emptyMap(Comparator<? super K> comparator) {

    assertEquals("foo", Iterators.getOnlyElement(iterator, "bar"));
  }

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

  public void testGetOnlyElement_withDefault_empty_null() {
    Iterator<String> iterator = Iterators.emptyIterator();

public final class Iterators {
  private Iterators() {}

  /**
   * Returns the empty iterator.
   *
   * <p>The {@link Iterable} equivalent of this method is {@link ImmutableSet#of()}.
   */
  static <T extends @Nullable Object> UnmodifiableIterator<T> emptyIterator() {
    return emptyListIterator();
  }

  /**
   * Returns the empty iterator.
   *

   * uses less memory than TreeMap; then say so in the class Javadoc.
   */
  private static final Comparator<?> NATURAL_ORDER = Ordering.natural();

  private static final ImmutableSortedMap<Comparable<?>, Object> NATURAL_EMPTY_MAP =
      new ImmutableSortedMap<>(
          ImmutableSortedSet.emptySet(Ordering.natural()), ImmutableList.<Object>of());

  static <K, V> ImmutableSortedMap<K, V> emptyMap(Comparator<? super K> comparator) {

   * provided, and they should not use soft, weak, or phantom references.
   *
   * @param map place to store the mapping from each key to its corresponding values
   * @param factory supplier of new, empty lists that will each hold all values for a given key
   * @throws IllegalArgumentException if {@code map} is not empty
   */