CODE:

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, trailer; private int size = 0; public DoublyLinkedList() { header = new Node(null, null, null); trailer = new Node(null, 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 Node(e, 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(); } //To Be Completed!!!!!!!!!!!!!!!!!!!!!!!!!!!! public void method4test() { } } public class GameEntry { private String name; private int score; public GameEntry(String n, int s) { name = n; score = s; } public String getName() { return name; } public int getScore() { return score; } public String toString() { return "(" + name + ", " + score + ")"; } }

import java.util.Scanner;

public class DoublyLinkedListTest{ public static void main(String[] args) { DoublyLinkedList []listGE = new DoublyLinkedList [4]; String[] names = {"A", "B", "C", "D", "E", "F", "G", "H"}; int[] scores = {7, 1, 5, 4, 8, 6, 2, 9}; GameEntry [] gE = new GameEntry[8]; for (int i = 0; i (); //Testing addlast()... for (int i = 0; i For this lab, the following classes are given for this test (with what you need to do): GameEntry: the same as in the textbook/assignments/projects. DoublyLinkedList: you are to reimplement the following methods without using method addBetween: addFirst o addLast (before working on the reimplementation, you would need to understand, or better, reimplement, the methods addBetween and remove!!). Many of the methods in the class use method addBetween-practice of reimplementing those methods without using method addBetween! DoublyLinkedListTest: this is a incomplete class, you would add more testing code like the one in this class, to test the following methods given in class DoublyLinkedList: o addFirst o removeFirst o remove Last Design and implement the test class (as suggested in the test class comments) so as to fully test the methods correctly