* @return a set of entries representing the data of this multiset
   */
  Set<Entry<E>> entrySet();

  /**
   * An unmodifiable element-count pair for a multiset. The {@link Multiset#entrySet} method returns
   * a view of the multiset whose elements are of this class. A multiset implementation may return
   * Entry instances that are either live "read-through" views to the Multiset, or immutable

   * @return a set of entries representing the data of this multiset
   */
  Set<Entry<E>> entrySet();

  /**
   * An unmodifiable element-count pair for a multiset. The {@link Multiset#entrySet} method returns
   * a view of the multiset whose elements are of this class. A multiset implementation may return
   * Entry instances that are either live "read-through" views to the Multiset, or immutable

   * <p>Results are undefined if {@code multiset1} and {@code multiset2} are based on different
   * equivalence relations (as {@code HashMultiset} and {@code TreeMultiset} are).
   *
   * @since 14.0
   */
  public static <E extends @Nullable Object> Multiset<E> union(
      final Multiset<? extends E> multiset1, final Multiset<? extends E> multiset2) {
    checkNotNull(multiset1);
    checkNotNull(multiset2);

   * <p>Results are undefined if {@code multiset1} and {@code multiset2} are based on different
   * equivalence relations (as {@code HashMultiset} and {@code TreeMultiset} are).
   *
   * @since 14.0
   */
  public static <E extends @Nullable Object> Multiset<E> union(
      final Multiset<? extends E> multiset1, final Multiset<? extends E> multiset2) {
    checkNotNull(multiset1);
    checkNotNull(multiset2);

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

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

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

    return Collector.of(
        () -> TreeMultiset.create(comparator),
        (multiset, t) -> mapAndAdd(t, multiset, elementFunction, countFunction),
        (multiset1, multiset2) -> {
          multiset1.addAll(multiset2);
          return multiset1;
        },
        (Multiset<E> multiset) -> copyOfSortedEntries(comparator, multiset.entrySet()));
  }

  @SuppressWarnings("Java7ApiChecker")

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

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

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

  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;
  }

  /**

  }

  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);