int index = headIndex(element, true) - 1;
    return (index == -1) ? null : elements.get(index);
  }

  @Override
  public @Nullable E ceiling(E element) {
    int index = tailIndex(element, true);
    return (index == size()) ? null : elements.get(index);
  }

  @Override
  public @Nullable E higher(E element) {
    int index = tailIndex(element, false);

    return new LexicographicalOrdering<S>(checkNotNull(comparator));
  }

  /**
   * Returns {@code true} if each element in {@code iterable} after the first is greater than or
   * equal to the element that preceded it, according to the specified comparator. Note that this is
   * always true when the iterable has fewer than two elements.
   */
  public static <T extends @Nullable Object> boolean isInOrder(

    multimap.put(2, "foo");
    for (String element : elements) {
      multimap.put(3, element);
    }
  }

  static void populateMultimapForKeySet(Multimap<String, Integer> multimap, String[] elements) {
    for (String element : elements) {
      multimap.put(element, 2);
      multimap.put(element, 3);
    }
  }

   *
   * @param elements the collection of elements to be checked for containment in this multiset
   * @return {@code true} if this multiset contains at least one occurrence of each element
   *     contained in {@code elements}
   * @throws NullPointerException if {@code elements} is null
   */
  @Override
  boolean containsAll(Collection<?> elements);

  /**
   * {@inheritDoc}
   *

   *
   * @param elements the collection of elements to be checked for containment in this multiset
   * @return {@code true} if this multiset contains at least one occurrence of each element
   *     contained in {@code elements}
   * @throws NullPointerException if {@code elements} is null
   */
  @Override
  boolean containsAll(Collection<?> elements);

  /**
   * {@inheritDoc}
   *

   * unspecified order.
   *
   * @param elements the elements that the set should contain
   * @return a new {@code CompactHashSet} containing those elements (minus duplicates)
   */
  @SafeVarargs
  public static <E extends @Nullable Object> CompactHashSet<E> create(E... elements) {
    CompactHashSet<E> set = createWithExpectedSize(elements.length);

    @Override
    protected List<Float> create(Float[] elements) {
      return asList(elements);
    }
  }

  public static final class FloatsAsListHeadSubListGenerator extends TestFloatListGenerator {
    @Override
    protected List<Float> create(Float[] elements) {
      Float[] suffix = {Float.MIN_VALUE, Float.MAX_VALUE};
      Float[] all = concat(elements, suffix);
      return asList(all).subList(0, elements.length);

    @Override
    protected List<Float> create(Float[] elements) {
      return asList(elements);
    }
  }

  public static final class FloatsAsListHeadSubListGenerator extends TestFloatListGenerator {
    @Override
    protected List<Float> create(Float[] elements) {
      Float[] suffix = {Float.MIN_VALUE, Float.MAX_VALUE};
      Float[] all = concat(elements, suffix);
      return asList(all).subList(0, elements.length);

    @Override
    protected List<Integer> create(Integer[] elements) {
      return asList(elements);
    }
  }

  public static final class IntsAsListHeadSubListGenerator extends TestIntegerListGenerator {
    @Override
    protected List<Integer> create(Integer[] elements) {
      Integer[] suffix = {Integer.MIN_VALUE, Integer.MAX_VALUE};
      Integer[] all = concat(elements, suffix);
      return asList(all).subList(0, elements.length);

            + " even if some elements are null.",
        getSet().equals(MinimalSet.from(elements)));
  }

  @CollectionSize.Require(absent = CollectionSize.ZERO)
  public void testEquals_otherContainsNull() {
    Collection<E> elements = getSampleElements(getNumElements() - 1);
    elements.add(null);
    Set<E> other = MinimalSet.from(elements);

    assertFalse(