iterator.next();
    }
    return iterator.next();
  }

  private static final class EntryComparator<K extends @Nullable Object, V extends @Nullable Object>
      implements Comparator<Entry<K, V>> {
    final @Nullable Comparator<? super K> keyComparator;

    EntryComparator(@Nullable Comparator<? super K> keyComparator) {
      this.keyComparator = keyComparator;
    }

    @Override