}

  @Override
  int nextIndex(int index) {
    int result = getSuccessor(index);
    return (result == ENDPOINT) ? -1 : result;
  }

  @Override
  int nextIndexAfterRemove(int oldNextIndex, int removedIndex) {
    return (oldNextIndex == size()) ? removedIndex : oldNextIndex;
  }

  private int getPredecessor(int entry) {
    return (int) (links[entry] >>> 32);
  }

    @Override
    public void remove() {
      checkForConcurrentModification();
      CollectPreconditions.checkRemove(toRemove != -1);
      size -= backingMap.removeEntry(toRemove);
      entryIndex = backingMap.nextIndexAfterRemove(entryIndex, toRemove);
      toRemove = -1;
      expectedModCount = backingMap.modCount;
    }
  }

  @Override
  final Iterator<E> elementIterator() {
    return new Itr<E>() {