* MultimapBuilder#treeKeys()}, may make additional guarantees.
   */
  @Override
  Map<K, Collection<V>> asMap();

  /**
   * Returns the comparator that orders the multimap values, with {@code null} indicating that
   * natural ordering is used.
   */
  @Nullable Comparator<? super V> valueComparator();

  }

  static <T extends @Nullable Object> Spliterator<T> indexed(
      int size,
      int extraCharacteristics,
      IntFunction<T> function,
      @Nullable Comparator<? super T> comparator) {
    if (comparator != null) {
      checkArgument((extraCharacteristics & Spliterator.SORTED) != 0);
    }
    final class WithCharacteristics implements Spliterator<T> {
      private final Spliterator.OfInt delegate;

    checkNotNull(values);
    if (values instanceof SortedSet) {
      SortedSet<C> set = (SortedSet<C>) values;
      Comparator<?> comparator = set.comparator();
      if (Ordering.<C>natural().equals(comparator) || comparator == null) {
        return closed(set.first(), set.last());
      }
    }
    Iterator<C> valueIterator = values.iterator();

    Collections.addAll(tmp, elements);
    return tmp.toArray(new String[0]);
  }

  static <T> Comparator<T> arbitraryNullFriendlyComparator() {
    return new NullFriendlyComparator<>();
  }

  private static final class NullFriendlyComparator<T> implements Comparator<T>, Serializable {
    @Override
    public int compare(T left, T right) {

      return notSubtype(shop);
    }

    @TestSubtype(suppressGetSubtype = true)
    public Comparator<Electronics> supertypeIsTopLevelClass(
        Mall<Indoor>.Retailer<Electronics> shop) {
      return isSubtype(shop);
    }

    @TestSubtype
    public Comparator<Electronics> topLevelClassIsNotSupertypeDueToTypeParameter(
        Mall<Indoor>.Retailer<Grocery> shop) {

            new char[] {GREATEST, GREATEST, GREATEST});

    Comparator<char[]> comparator = Chars.lexicographicalComparator();
    Helpers.testComparator(comparator, ordered);
  }

  @J2ktIncompatible
  @GwtIncompatible // SerializableTester
  public void testLexicographicalComparatorSerializable() {
    Comparator<char[]> comparator = Chars.lexicographicalComparator();

  }

  public static <E> ImmutableList<E> sortedCopyOf(
      Comparator<? super E> comparator, Iterable<? extends E> elements) {
    checkNotNull(comparator);
    @SuppressWarnings("unchecked") // all supported methods are covariant
    E[] array = (E[]) Iterables.toArray(elements);
    checkElementsNotNull(array);
    Arrays.sort(array, comparator);
    return asImmutableList(array);
  }

            new long[] {GREATEST, GREATEST - 1L},
            new long[] {GREATEST, GREATEST},
            new long[] {GREATEST, GREATEST, GREATEST});

    Comparator<long[]> comparator = UnsignedLongs.lexicographicalComparator();
    Helpers.testComparator(comparator, ordered);
  }

  public void testSort() {
    testSort(new long[] {}, new long[] {});
    testSort(new long[] {2}, new long[] {2});

  }

  static <T extends @Nullable Object> Spliterator<T> indexed(
      int size,
      int extraCharacteristics,
      IntFunction<T> function,
      @Nullable Comparator<? super T> comparator) {
    if (comparator != null) {
      checkArgument((extraCharacteristics & Spliterator.SORTED) != 0);
    }
    /*
     * @IgnoreJRERequirement should be redundant with the one on Streams itself, but it's necessary

      assertEquals(multimap().valueComparator(), valueSet.comparator());
    }
  }

  public void testAsMapGetImplementsSortedSet() {
    for (K key : multimap().keySet()) {
      SortedSet<V> valueSet = (SortedSet<V>) multimap().asMap().get(key);
      assertEquals(multimap().valueComparator(), valueSet.comparator());
    }
  }

  @MapFeature.Require(SUPPORTS_REMOVE)