}

  @CheckForNull @LazyInit private transient Reference<Multiset<N>> adjacentNodesReference;

  @Override
  public Set<N> adjacentNodes() {
    return Collections.unmodifiableSet(adjacentNodesMultiset().elementSet());
  }

  private Multiset<N> adjacentNodesMultiset() {
    Multiset<N> adjacentNodes = getReference(adjacentNodesReference);
    if (adjacentNodes == null) {

   *
   * @param elements the elements that the multiset should contain
   */
  public static <E extends @Nullable Object> HashMultiset<E> create(
      Iterable<? extends E> elements) {
    HashMultiset<E> multiset = create(Multisets.inferDistinctElements(elements));
    Iterables.addAll(multiset, elements);
    return multiset;
  }

  HashMultiset(int distinctElements) {

    Multiset<E> multiset = LinkedHashMultiset.create();
    Iterators.addAll(multiset, elements);
    return copyFromEntries(multiset.entrySet());
  }

  private static <E> ImmutableMultiset<E> copyFromElements(E... elements) {
    Multiset<E> multiset = LinkedHashMultiset.create();
    Collections.addAll(multiset, elements);
    return copyFromEntries(multiset.entrySet());
  }

  }

  public void testEmptyRangeSubMultiset(SortedMultiset<E> multiset) {
    assertTrue(multiset.isEmpty());
    assertEquals(0, multiset.size());
    assertEquals(0, multiset.toArray().length);
    assertTrue(multiset.entrySet().isEmpty());
    assertFalse(multiset.iterator().hasNext());
    assertEquals(0, multiset.entrySet().size());
    assertEquals(0, multiset.entrySet().toArray().length);

  public void testCreation_noArgs() {
    Multiset<String> multiset = ImmutableSortedMultiset.of();
    assertTrue(multiset.isEmpty());
  }

  public void testCreation_oneElement() {
    Multiset<String> multiset = ImmutableSortedMultiset.of("a");
    assertEquals(HashMultiset.create(asList("a")), multiset);
  }

  public void testCreation_twoElements() {
    Multiset<String> multiset = ImmutableSortedMultiset.of("a", "b");

   *
   * @param elements the elements that the multiset should contain
   */
  public static <E> ConcurrentHashMultiset<E> create(Iterable<? extends E> elements) {
    ConcurrentHashMultiset<E> multiset = ConcurrentHashMultiset.create();
    Iterables.addAll(multiset, elements);
    return multiset;
  }

  /**

   * result in an {@link UnsupportedOperationException}.
   *
   * <p>The returned multiset will be serializable if the specified multiset is serializable.
   *
   * @param multiset the multiset for which an unmodifiable view is to be generated
   * @return an unmodifiable view of the multiset
   */
  public static <E extends @Nullable Object> Multiset<E> unmodifiableMultiset(

   * result in an {@link UnsupportedOperationException}.
   *
   * <p>The returned multiset will be serializable if the specified multiset is serializable.
   *
   * @param multiset the multiset for which an unmodifiable view is to be generated
   * @return an unmodifiable view of the multiset
   */
  public static <E extends @Nullable Object> Multiset<E> unmodifiableMultiset(

    FEMALE
  }

  public void testClassCreate() {
    Multiset<Color> ms = EnumMultiset.create(Color.class);
    ms.add(Color.RED);
    ms.add(Color.YELLOW);
    ms.add(Color.RED);
    assertEquals(0, ms.count(Color.BLUE));
    assertEquals(1, ms.count(Color.YELLOW));
    assertEquals(2, ms.count(Color.RED));
  }

  public void testCollectionCreate() {

/**
 * Optional features of classes derived from {@link Multiset}.
 *
 * @author Louis Wasserman
 */
@SuppressWarnings("rawtypes") // maybe avoidable if we rework the whole package?
@GwtCompatible
public enum MultisetFeature implements Feature<Multiset> {
  /**
   * Indicates that elements from {@code Multiset.entrySet()} update to reflect changes in the
   * backing multiset.
   */
  ENTRIES_ARE_VIEWS;

  @Override