The implementation of several methods is (or can be) the same between our ArrayList and LinkedList. Write a common abstract superclass called AbstractList that implements the common behavior and is extended by both ArrayList and LinkedList. Factor out the common code from the two list classes into this abstract superclass so that no code duplication occurs between the two. Use iterators wherever possible in the abstract code to ensure that the implementation is efficient for both types of lists.

(Just want you to create an abstract class of

public E get(int index);

and

public int indexOf(E value);

Below you will first find the public E get(int index) { of ArrayList.java then public int indexOf(E value) { of ArrayList.java then public E get(int index) { of LinkedList.java and then public int indexOf(E value) { of LinkedList.java. I also have added comments on top of the code so you do not have any problems figuring out which code is which one.

IF YOU DON'T KNOW HOW TO DO IT, THEN PLEASE LEAVE IT FOR SOMEONE WHO KNOWS HOW TO DO IT PROPERLY.

import java.util.*;

// pre : 0 <= index < size() (throws IndexOutOfBoundsException if not) // post: returns the value at the given index in the list //ArrayList.java

public E get(int index) { checkIndex(index); return elementData[index]; // post: creates a comma-separated, bracketed version of the list public String toString() { if (size == 0) { return "[]"; } else { String result = "[" + elementData[0]; for (int i = 1; i < size; i++) { result += ", " + elementData[i]; } result += "]"; return result; } } // post : returns the position of the first occurrence of the given // value (-1 if not found) //ArrayList.java

public int indexOf(E value) { for (int i = 0; i < size; i++) { if (elementData[i].equals(value)) { return i; } } return -1; }

// pre : 0 <= index < size() (throws IndexOutOfBoundsException if not) // post: returns the value at the given index in the list //LinkedList.java

public E get(int index) { checkIndex(index); ListNode current = nodeAt(index); return current.data; }

// post: creates a comma-separated, bracketed version of the list public String toString() { if (size == 0) { return "[]"; } else { String result = "[" + front.next.data; ListNode current = front.next.next; while (current != back) { result += ", " + current.data; current = current.next; } result += "]"; return result; } }

// post : returns the position of the first occurrence of the given // value (-1 if not found) //LinkedList.java

public int indexOf(E value) { int index = 0; ListNode current = front.next; while (current != back) { if (current.data.equals(value)) { return index; } index++; current = current.next; } return -1; }