checkState(Objects.equal(value, get(getKey())), "entry no longer in map");
      updateInverseMap(getKey(), true, oldValue, value);
      return oldValue;
    }
  }

  Iterator<Entry<K, V>> entrySetIterator() {
    final Iterator<Entry<K, V>> iterator = delegate.entrySet().iterator();
    return new Iterator<Entry<K, V>>() {
      @CheckForNull Entry<K, V> entry;

      @Override
      public boolean hasNext() {