@GwtCompatible(emulated = true)
@ElementTypesAreNonnullByDefault
public final class HashBiMap<K extends @Nullable Object, V extends @Nullable Object>
    extends IteratorBasedAbstractMap<K, V> implements BiMap<K, V>, Serializable {

  /** Returns a new, empty {@code HashBiMap} with the default initial capacity (16). */
  public static <K extends @Nullable Object, V extends @Nullable Object> HashBiMap<K, V> create() {
    return create(16);
  }

  /**

  @SuppressWarnings({"AndroidJdkLibsChecker", "Java7ApiChecker"})
  @IgnoreJRERequirement // Users will use this only if they're already using streams.
  @Beta // TODO: b/288085449 - Remove.
  public static <T extends @Nullable Object, E extends @Nullable Object, M extends Multiset<E>>
      Collector<T, ?, M> toMultiset(
          Function<? super T, E> elementFunction,
          ToIntFunction<? super T> countFunction,
          Supplier<M> multisetSupplier) {

    assertMultimapRemainsUnmodified(multimap, originalEntries);
  }

  private static <E extends @Nullable Object> void assertCollectionsAreEquivalent(
      Collection<E> expected, Collection<E> actual) {
    assertIteratorsInOrder(expected.iterator(), actual.iterator());
  }

  private static <K extends @Nullable Object, V extends @Nullable Object>
      void assertMultimapRemainsUnmodified(Multimap<K, V> expected, List<Entry<K, V>> actual) {

  // stored in the builder, which may use it to throw an exception later.
  static <K, V> RegularImmutableMap<K, V> create(
      int n, @Nullable Object[] alternatingKeysAndValues, @Nullable Builder<K, V> builder) {
    if (n == 0) {
      @SuppressWarnings("unchecked")
      RegularImmutableMap<K, V> empty = (RegularImmutableMap<K, V>) EMPTY;
      return empty;

 */
@GwtCompatible
@ElementTypesAreNonnullByDefault
public final class HashBiMap<K extends @Nullable Object, V extends @Nullable Object>
    extends AbstractMap<K, V> implements BiMap<K, V>, Serializable {

  /** Returns a new, empty {@code HashBiMap} with the default initial capacity (16). */
  public static <K extends @Nullable Object, V extends @Nullable Object> HashBiMap<K, V> create() {
    return create(16);
  }

  /**

              }

              @Override
              public boolean equals(@Nullable Object o) {
                return map.equals(o);
              }

              @Override
              public String toString() {
                return map.toString();
              }

              @Override
              public @Nullable String remove(Object key) {
                return map.remove(key);
              }

    @Override
    public boolean equals(@Nullable Object o) {
      return false;
    }

    @Override
    public int hashCode() {
      return super.hashCode();
    }
  }

  /** Test class that returns true if the test object is null */
  private static class InvalidEqualsNullObject {

    @Override
    public boolean equals(@Nullable Object o) {
      return o == this || o == null;
    }

              }

              @Override
              public boolean equals(@Nullable Object o) {
                return map.equals(o);
              }

              @Override
              public String toString() {
                return map.toString();
              }

              @Override
              public @Nullable String remove(Object key) {
                return map.remove(key);
              }

      Optional<String> unused =
          Optional.of("a")
              .transform(
                  (Function<String, String>)
                      new Function<String, @Nullable String>() {
                        @Override
                        public @Nullable String apply(String input) {
                          return null;
                        }
                      });
      fail("Should throw if Function returns null.");

      final Runnable runnable;
      final Executor executor;
      // Volatile because this is written on one thread and read on another with no synchronization.
      @Nullable volatile RunnableExecutorPair next;

      RunnableExecutorPair(@Nullable Runnable runnable, @Nullable Executor executor) {
        this.runnable = runnable;
        this.executor = executor;
      }

      void execute() {
        try {