Iterating from the end of a list

Question

I know that we can iterate over the list in the reverse order as follows:

List<Object> lst;
ListIterator<Object> i = lst.listIterator(lst.size());

But is it efficient if lst is a LinkedList? I mean when we obtain the ListIterator pointing to the end of the list, does the implementation iterate over the list from the begging to the list.size() position (takes O(n) time, where n is a size of the list)?

If it does, is there a way to avoid it?

Answer 1

The javadoc states that LinkedList is a doubly-linked list, so I would expect descendingIterator(), which return an iterator pointing to the tail of the list, to be O(1). Note that descendingIterator is from the Deque interface.

Now it is difficult to say whether the statement lst.listIterator(lst.size()) is also O(1), because it is not documented if listIterator method optimize the fact that the next element from lst.size() is the tail.