Exercise 24.3: (pg no.  971)
(Implement a doubly linked list) The MyLinkedList class used in Listing 24.5 is
a one-way directional linked list that enables one-way traversal of the list. Modify
the Node class to add the new data field name previous to refer to the previous
node in the list, as follows:
public class Node<E> {
E element;
Node<E> next;
Node<E> previous;
public Node(E e) {
element = e;
}
}
Implement a new class named TwoWayLinkedList that uses a doubly linked list
to store elements. Define TwoWayLinkedList to implements MyList. You need
to implement all the methods defined in MyLinkedList as well as the methods
listIterator() and listIterator(int index). Both return an instance of
java.util.ListIterator<E> (see Figure 20.4). The former sets the cursor to
the head of the list and the latter to the element at the specified index.