@Override
    protected List<V> delegate() {
      return emptyList();
    }
  }

  @Override
  Iterator<Entry<K, V>> entryIterator() {
    throw new AssertionError("should never be called");
  }

  @Override
  Collection<Entry<K, V>> createEntries() {
    return new Entries();
  }

  @WeakOuter

    final Iterator<Map<C, V>> mapIterator = backingMap.values().iterator();
    Iterator<Entry<C, V>> entryIterator = emptyIterator();

    @Override
    protected @Nullable C computeNext() {
      while (true) {
        if (entryIterator.hasNext()) {
          Entry<C, V> entry = entryIterator.next();
          if (!seen.containsKey(entry.getKey())) {
            seen.put(entry.getKey(), entry.getValue());

   *
   * <p>In particular, this map iterates over entries with repeated calls to {@link
   * NavigableMap#lowerEntry}. If a more efficient means of iteration is available, you may wish to
   * override the {@code entryIterator()} method of this class.
   *
   * @since 12.0
   */
  protected class StandardDescendingMap extends Maps.DescendingMap<K, V> {
    /** Constructor for use by subclasses. */
    public StandardDescendingMap() {}

   */
  protected @Nullable V standardRemove(@Nullable Object key) {
    Iterator<Entry<K, V>> entryIterator = entrySet().iterator();
    while (entryIterator.hasNext()) {
      Entry<K, V> entry = entryIterator.next();
      if (Objects.equals(entry.getKey(), key)) {
        V value = entry.getValue();
        entryIterator.remove();
        return value;
      }
    }
    return null;
  }

  /**

          Iterator<Entry<K, V>> entryIterator) {
    return new UnmodifiableIterator<Entry<K, V>>() {
      @Override
      public boolean hasNext() {
        return entryIterator.hasNext();
      }

      @Override
      public Entry<K, V> next() {
        return unmodifiableEntry(entryIterator.next());
      }
    };
  }

   *
   * <p>In particular, this map iterates over entries with repeated calls to {@link
   * NavigableMap#lowerEntry}. If a more efficient means of iteration is available, you may wish to
   * override the {@code entryIterator()} method of this class.
   *
   * @since 12.0
   */
  protected class StandardDescendingMap extends Maps.DescendingMap<K, V> {
    /** Constructor for use by subclasses. */
    public StandardDescendingMap() {}

    Entry<String, String> firstEntry = entries.iterator().next();
    entries.remove(firstEntry);
    assertFalse(underlying.containsKey("f"));

    Iterator<Entry<String, String>> entryIterator = entries.iterator();
    entryIterator.next();
    entryIterator.remove();
    assertFalse(underlying.containsKey("g"));

    assertTrue(underlying.isEmpty());
    assertTrue(map.isEmpty());
    assertTrue(keys.isEmpty());

    @Nullable Entry<K, Collection<V>> pollAsMapEntry(
        Iterator<Entry<K, Collection<V>>> entryIterator) {
      if (!entryIterator.hasNext()) {
        return null;
      }
      Entry<K, Collection<V>> entry = entryIterator.next();
      Collection<V> output = createCollection();
      output.addAll(entry.getValue());
      entryIterator.remove();
      return immutableEntry(entry.getKey(), unmodifiableCollectionSubclass(output));

      Integer keyIndex = keyToIndex().get(key);
      return (keyIndex == null) ? null : getValue(keyIndex);
    }

    @Override
    UnmodifiableIterator<Entry<K, V>> entryIterator() {
      return new AbstractIterator<Entry<K, V>>() {
        private int index = -1;
        private final int maxIndex = keyToIndex().size();

        @Override

          Iterator<Entry<K, V>> entryIterator) {
    return new UnmodifiableIterator<Entry<K, V>>() {
      @Override
      public boolean hasNext() {
        return entryIterator.hasNext();
      }

      @Override
      public Entry<K, V> next() {
        return unmodifiableEntry(entryIterator.next());
      }
    };
  }