Exercise $2$

In the existing DoublyLinkedList class, write and test a non$-$static method named reverseList to

reverse a doubly linked list. Write the testing code in the main method of the class

DoublyLinkedList. For this purpose, you must only use and update the DoublyLinkedList.java

file provided in Lesson$2$Examples posted in the eCentennial module "Lesson Examples $($from

textbook$)"$

Code:

package ex$2$;

public class DoublyLinkedList $\{$

private static class Node $\{$

private E element;

private Node prev;

private Node next;

public Node$($E e$,$ Node p$,$ Node n$)\{$

element $=$ e;

prev $=$ p;

next $=$ n;

$\}$

public E getElement$()\{$ return element; $\}$

public Node getPrev$()\{$ return prev; $\}$

public Node getNext$()\{$ return next; $\}$

public void setPrev$($Node p$)\{$ prev $=$ p; $\}$

public void setNext$($Node n$)\{$ next $=$ n; $\}$

$\}$

private Node header;

private Node trailer;

private int size $=0$;

public DoublyLinkedList$()\{$

header $=$ new Nodenull$,$ null, null$)$;

trailer $=$ new Nodenull$,$ header, null$)$;

header.setNext$($trailer$)$;

$\}$

public int size$()\{$ return size; $\}$

public boolean isEmpty$()\{$ return size $==0$; $\}$

public E first$()\{$

if $($isEmpty$())$ return null;

return header.getNext$().$getElement$()$;

$\}$

public E last$()\{$

if $($isEmpty$())$ return null;

return trailer.getPrev$().$getElement$()$;

$\}$

public void addFirst$($E e$)\{$

addBetween$($e$,$ header, header.getNext$())$;

$\}$

public void addLast$($E e$)\{$

addBetween$($e$,$ trailer.getPrev$(),$ trailer$)$;

$\}$

public E removeFirst$()\{$

if $($isEmpty$())$ return null;

return remove$($header$.$getNext$())$;

$\}$

public E removeLast$()\{$

if $($isEmpty$())$ return null;

return remove$($trailer$.$getPrev$())$;

$\}$

private void addBetween$($E e$,$ Node predecessor, Node successor$)\{$

Node newest $=$ new Nodee$,$ predecessor, successor$)$;

predecessor.setNext$($newest$)$;

successor.setPrev$($newest$)$;

size$++$;

$\}$

private E remove$($Node node$)\{$

Node predecessor $=$ node.getPrev$()$;

Node successor $=$ node.getNext$()$;

predecessor.setNext$($successor$)$;

successor.setPrev$($predecessor$)$;

size$--$;

return node.getElement$()$;

$\}$

public String toString$()\{$

StringBuilder sb $=$ new StringBuilder$("(")$;

Node walk $=$ header.getNext$()$;

while $($walk $!=$ trailer$)\{$

sb$.$append$($walk$.$getElement$())$;

walk $=$ walk.getNext$()$;

if $($walk $!=$ trailer$)$

sb$.$append$(",")$;

$\}$

sb$.$append$(")")$;

return sb$.$toString$()$;

$\}$

public static void main$($String$[]$ args$)$

$\{$

DoublyLinkedList list $=$ new DoublyLinkedList$()$;

list.addFirst$("$MSP$")$;

list.addLast$("$ATL$")$;

list.addLast$("$BOS$")$;

list.addFirst$("$LAX$")$;

System.out.println$("$Original list: $"+$ list.toString$())$;

System.out.println$("$Reversed list: $"+$ list.toString$())$;

System.out.println$($list$)$;

System.out.println$($list$.$first$())$;

$\}$

$\}$