@ElementTypesAreNonnullByDefault
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.

@ElementTypesAreNonnullByDefault
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 create(ObjectCountHashMap.DEFAULT_SIZE);
  }

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

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

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

            .named("HashMultiset")
            .createTestSuite());
    suite.addTestSuite(HashMultisetTest.class);
    return suite;
  }

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

    assertEquals(HashMultiset.create(asList("a", "b", "a")), multiset);
    assertEquals(1, iterable.count);
  }

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

  @Param({"0", "1", "16", "256", "4096", "65536"})
  int size;

  LinkedHashMultiset<Object> linkedHashMultiset;
  HashMultiset<Object> hashMultiset;

  // TreeMultiset requires a Comparable element.
  TreeMultiset<Integer> treeMultiset;

  @BeforeExperiment
  void setUp() {
    hashMultiset = HashMultiset.create(size);
    linkedHashMultiset = LinkedHashMultiset.create(size);
    treeMultiset = TreeMultiset.create();

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

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

    assertEquals(HashMultiset.create(asList("a", "b", "a")), multiset);
    assertEquals(1, iterable.count);
  }

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

  @Param({"0", "1", "16", "256", "4096", "65536"})
  int size;

  LinkedHashMultiset<Object> linkedHashMultiset;
  HashMultiset<Object> hashMultiset;

  // TreeMultiset requires a Comparable element.
  TreeMultiset<Integer> treeMultiset;

  @BeforeExperiment
  void setUp() {
    hashMultiset = HashMultiset.create(size);
    linkedHashMultiset = LinkedHashMultiset.create(size);
    treeMultiset = TreeMultiset.create();

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

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