You are provided an implementation singly-linked list and a partially implemented Iterator class. Starting with this implementation, modify it so that it is a doubly-linked list, and finish the implementation of a class for an Iterator that can traverse this list both forwards and backwards. public class LinkedList {

Node itsFirstNode;
Node itsLastNode;
private int size;

public LinkedList() {
itsFirstNode = null;
itsLastNode = null;
size = 0;
}

public int size() {
return this. size;
}

public Iterator getIterator() {
return new Iterator(this);
}