* @since 2.0
 */
@GwtCompatible
public final class HashMultiset<E extends @Nullable Object> extends AbstractMapBasedMultiset<E> {

  /** Creates a new, empty {@code HashMultiset} using the default initial capacity. */
  public static <E extends @Nullable Object> HashMultiset<E> create() {
    return new HashMultiset<>();
  }

  /**
   * Creates a new, empty {@code HashMultiset} with the specified expected number of distinct
   * elements.

    Multiset<String> multiset = HashMultiset.create();
    Multiset<String> toRemove = HashMultiset.create(asList("a", "b", "a"));
    assertFalse(Multisets.removeOccurrences(multiset, toRemove));
    assertTrue(multiset.isEmpty());
  }

  public void testUnion() {
    Multiset<String> ms1 = HashMultiset.create(asList("a", "b", "a"));
    Multiset<String> ms2 = HashMultiset.create(asList("a", "b", "b", "c"));

    return new TestStringMultisetGenerator() {
      @Override
      protected Multiset<String> create(String[] elements) {
        return HashMultiset.create(asList(elements));
      }
    };
  }

  public void testCreate() {
    Multiset<String> multiset = HashMultiset.create();
    multiset.add("foo", 2);
    multiset.add("bar");
    assertEquals(3, multiset.size());
    assertEquals(2, multiset.count("foo"));
  }

    Multiset<String> c = HashMultiset.create();
    Multiset<String> multiset = ImmutableMultiset.copyOf(c);
    assertTrue(multiset.isEmpty());
  }

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

    Multiset<String> c = HashMultiset.create();
    Multiset<String> multiset = ImmutableMultiset.copyOf(c);
    assertTrue(multiset.isEmpty());
  }

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

    return new TestStringMultisetGenerator() {
      @Override
      protected Multiset<String> create(String[] elements) {
        return HashMultiset.create(asList(elements));
      }
    };
  }

  public void testCreate() {
    Multiset<String> multiset = HashMultiset.create();
    multiset.add("foo", 2);
    multiset.add("bar");
    assertEquals(3, multiset.size());
    assertEquals(2, multiset.count("foo"));
  }

    return Multisets.immutableEntry(element, count);
  }

  private static <E extends @Nullable Object> Entry<E> control(E element, int count) {
    return HashMultiset.create(nCopies(count, element)).entrySet().iterator().next();
  }

  public void testToString() {
    assertEquals("foo", entry("foo", 1).toString());
    assertEquals("bar x 2", entry("bar", 2).toString());
  }

  @Generates
  static <E> Multiset<E> generateMultiset(@Nullable E freshElement) {
    return generateHashMultiset(freshElement);
  }

  @Generates
  static <E> HashMultiset<E> generateHashMultiset(@Nullable E freshElement) {
    HashMultiset<E> multiset = HashMultiset.create();
    multiset.add(freshElement);
    return multiset;
  }

  @Generates

    SerializableTester.reserializeAndAssert(multimap.asMap());
    Collection<Integer> valuesCopy = SerializableTester.reserialize(multimap.values());
    assertEquals(HashMultiset.create(multimap.values()), HashMultiset.create(valuesCopy));
  }

  @J2ktIncompatible
  @GwtIncompatible // SerializableTester
  public void testEmptySerialization() {

    SerializableTester.reserializeAndAssert(multimap.asMap());
    Collection<Integer> valuesCopy = SerializableTester.reserialize(multimap.values());
    assertEquals(HashMultiset.create(multimap.values()), HashMultiset.create(valuesCopy));
  }

  @J2ktIncompatible
  @GwtIncompatible // SerializableTester
  public void testEmptySerialization() {