extends Sets.ImprovedAbstractSet<Entry<E>> {
    abstract Multiset<E> multiset();

    @Override
    public boolean contains(@CheckForNull Object o) {
      if (o instanceof Entry) {
        Entry<?> entry = (Entry<?>) o;
        if (entry.getCount() <= 0) {
          return false;
        }
        int count = multiset().count(entry.getElement());
        return count == entry.getCount();

  static <K extends @Nullable Object, V extends @Nullable Object> Entry<V, K> reverseEntry(
      Entry<K, V> entry) {
    return mapEntry(entry.getValue(), entry.getKey());
  }

  @Override
  protected void expectContents(Collection<Entry<K, V>> expected) {
    super.expectContents(expected);
    List<Entry<V, K>> reversedEntries = new ArrayList<>();
    for (Entry<K, V> entry : expected) {
      reversedEntries.add(reverseEntry(entry));

      int expectedEntrySetHash = 0;
      for (Entry<K, V> entry : entrySet) {
        assertTrue(map.containsKey(entry.getKey()));
        assertTrue(map.containsValue(entry.getValue()));
        int expectedHash =
            (entry.getKey() == null ? 0 : entry.getKey().hashCode())
                ^ (entry.getValue() == null ? 0 : entry.getValue().hashCode());
        assertEquals(expectedHash, entry.hashCode());

  @CollectionSize.Require(absent = ZERO)
  public void testRemovePropagatesToAsMapEntrySet() {
    List<Entry<K, V>> entries = copyToList(multimap().entries());
    for (Entry<K, V> entry : entries) {
      resetContainer();

      K key = entry.getKey();
      V value = entry.getValue();

      Iterator<Entry<K, Collection<V>>> asMapItr = multimap().asMap().entrySet().iterator();
      Collection<V> collection = null;

  @CollectionSize.Require(absent = ZERO)
  public void testRemovePropagatesToAsMapEntrySet() {
    List<Entry<K, V>> entries = copyToList(multimap().entries());
    for (Entry<K, V> entry : entries) {
      resetContainer();

      K key = entry.getKey();
      V value = entry.getValue();

      Iterator<Entry<K, Collection<V>>> asMapItr = multimap().asMap().entrySet().iterator();
      Collection<V> collection = null;

   *
   * <p><b>Warning:</b> If an existing entry with this value is removed, the key for that entry is
   * discarded and not returned.
   *
   * @param key the key with which the specified value is to be associated
   * @param value the value to be associated with the specified key
   * @return the value that was previously associated with the key, or {@code null} if there was no

    @SuppressWarnings("unchecked")
    Entry<String, String>[] array = (Entry<String, String>[]) new Entry<?, ?>[entries.length];
    int i = 0;
    for (Object o : entries) {
      @SuppressWarnings("unchecked")
      Entry<String, String> e = (Entry<String, String>) o;
      array[i++] = e;
    }
    return create(array);
  }

  protected abstract ListMultimap<String, String> create(Entry<String, String>[] entries);

  @Override

    @SuppressWarnings("unchecked")
    Entry<String, String>[] array = (Entry<String, String>[]) new Entry<?, ?>[entries.length];
    int i = 0;
    for (Object o : entries) {
      @SuppressWarnings("unchecked")
      Entry<String, String> e = (Entry<String, String>) o;
      array[i++] = e;
    }
    return create(array);
  }

  protected abstract SetMultimap<String, String> create(Entry<String, String>[] entries);

  @Override

        protected Entry next;

        /** 前のエントリ */
        protected Entry previous;

        Entry(final E element, final Entry next, final Entry previous) {
            this.element = element;
            this.next = next;
            this.previous = previous;
        }

        /**
         * 要素を返します。
         *
         * @return 要素
         */
        public E getElement() {

    Entry<K, V> entry = lastEntry();
    if (entry == null) {
      throw new NoSuchElementException();
    } else {
      return entry.getKey();
    }
  }

  @Override
  @CheckForNull
  public Entry<K, V> lowerEntry(@ParametricNullness K key) {
    return headMap(key, false).lastEntry();
  }

  @Override
  @CheckForNull
  public Entry<K, V> floorEntry(@ParametricNullness K key) {
    return headMap(key, true).lastEntry();