Set<Entry<K, V>> es = entrySet;
    return (es != null) ? es : (entrySet = new EntrySet(this));
  }

  /**
   * Custom Entry class used by EntryIterator.next(), that relays setValue changes to the underlying
   * map.
   */
  private final class WriteThroughEntry implements Entry<K, V> {
    final K key;
    V value;

    WriteThroughEntry(K key, V value) {
      this.key = checkNotNull(key);

    @Override
    public V next() {
      return nextEntry().getValue();
    }
  }

  /**
   * Custom Entry class used by EntryIterator.next(), that relays setValue changes to the underlying
   * map.
   */
  final class WriteThroughEntry implements Entry<K, V> {
    final K key; // non-null
    V value; // non-null

    WriteThroughEntry(K key, V value) {
      this.key = key;

    @Override
    public V next() {
      return nextEntry().getValue();
    }
  }

  /**
   * Custom Entry class used by EntryIterator.next(), that relays setValue changes to the underlying
   * map.
   */
  final class WriteThroughEntry implements Entry<K, V> {
    final K key; // non-null
    V value; // non-null

    WriteThroughEntry(K key, V value) {
      this.key = key;