List, Linkedlist, Arraylist in Java

Question

About the List, Linkedlist and Arraylist, which one is a one way list and which one is Doubly-linked list? And how could we reverse it?

Answer 1

• List
  An interface that merely defines behavior of lists.
  • ArrayList
    A List implementation, backed by an array . It is not a linked list .
  • LinkedList
    A List implementation, backed by an implementation of a doubly-linked list .

If you want a single-linked list, you'll have to write it yourself.

I should point out that making a single linked list that implements java.util.List is not easy. It requires you to have a ListIterator<E> , and part of the ListIterator specification is that you can traverse in either direction with methods hasPrevious , previous , and previousIndex . So to keep it both efficient and true to the single linked list mantra would be very difficult.

Answer 2

You can reverse any collection using Collections.reverse(..) . LinkedList (and any Deque ) has descendingIterator()