if (entry == null) {
      throw new NoSuchElementException();
    }
    return entry.getElement();
  }

  @CheckForNull
  private static <E extends @Nullable Object> E getElementOrNull(@CheckForNull Entry<E> entry) {
    return (entry == null) ? null : entry.getElement();
  }

          ToOptionalState::new,
          (state, o) -> state.add((o == null) ? NULL_PLACEHOLDER : o),
          ToOptionalState::combine,
          state -> {
            Object result = state.getElement();
            return (result == NULL_PLACEHOLDER) ? null : result;
          },
          Collector.Characteristics.UNORDERED);

  /**

  public Entry<E> pollFirstEntry() {
    Iterator<Entry<E>> entryIterator = entryIterator();
    if (entryIterator.hasNext()) {
      Entry<E> result = entryIterator.next();
      result = Multisets.immutableEntry(result.getElement(), result.getCount());
      entryIterator.remove();
      return result;
    }
    return null;
  }

  @Override
  @CheckForNull
  public Entry<E> pollLastEntry() {

  public Entry<E> pollFirstEntry() {
    Iterator<Entry<E>> entryIterator = entryIterator();
    if (entryIterator.hasNext()) {
      Entry<E> result = entryIterator.next();
      result = Multisets.immutableEntry(result.getElement(), result.getCount());
      entryIterator.remove();
      return result;
    }
    return null;
  }

  @Override
  @CheckForNull
  public Entry<E> pollLastEntry() {

        @SuppressWarnings("unchecked")
        Multiset.Entry<E> entry = (Entry<E>) o;
        checkArgument(
            elements.add(entry.getElement()), "Duplicate keys not allowed in EntrySetGenerator");
        for (int i = 0; i < entry.getCount(); i++) {
          contents.add(entry.getElement());
        }
      }
      return ((Multiset<E>) gen.create(contents.toArray())).entrySet();
    }

 *     System.out.println(indexed.getElement());
 * }
 * </pre>
 *
 * <pre>
 * import static org.codelibs.core.collection.IndexedIterator.*;
 * import static org.codelibs.core.io.LineIterator.*;
 *
 * BufferedReader reader = ...;
 * for (Indexed&lt;String%gt; indexed : indexed(iterable(reader))) {
 *     System.out.println(indexed.getIndex());
 *     System.out.println(indexed.getElement());
 * }
 * </pre>
 *

        @SuppressWarnings("unchecked")
        Multiset.Entry<E> entry = (Entry<E>) o;
        checkArgument(
            elements.add(entry.getElement()), "Duplicate keys not allowed in EntrySetGenerator");
        for (int i = 0; i < entry.getCount(); i++) {
          contents.add(entry.getElement());
        }
      }
      return ((Multiset<E>) gen.create(contents.toArray())).entrySet();
    }

     */
    public Indexed(final T element, final int index) {
        this.element = element;
        this.index = index;
    }

    /**
     * 要素を返します。
     *
     * @return 要素
     */
    public T getElement() {
        return element;
    }

    /**
     * インデックスを返します。
     *
     * @return インデックス
     */
    public int getIndex() {
        return index;
    }

          @Override
          @ParametricNullness
          public E getElement() {
            return mapEntry.getKey();
          }

          @Override
          public int getCount() {
            Count count = mapEntry.getValue();
            if (count == null || count.get() == 0) {
              Count frequency = backingMap.get(getElement());
              if (frequency != null) {

      Collection<? extends Entry<? extends E>> entries) {
    ImmutableMultiset.Builder<E> builder = new ImmutableMultiset.Builder<E>(entries.size());
    for (Entry<? extends E> entry : entries) {
      builder.addCopies(entry.getElement(), entry.getCount());
    }
    return builder.build();
  }

  ImmutableMultiset() {}

  @Override
  public UnmodifiableIterator<E> iterator() {