Question

Please help with the codes for the implementation of java.util.List, specifically for the 3 below overridden methods

@Override

       public int lastIndexOf(Object arg0) { required code }

       @Override

       public ListIterator<R> listIterator() { required code }

       @Override

       public ListIterator<R> listIterator(int arg0) { required code }

PLEASE NOTE:

Below are some of other overridden methods that are already implemented, they are meant to be examples of what the answers to the above questions for the 3 methods should look like.

public void add(int index, R r) {

             if (index < 0 || index >= size()) {

                    throw new IndexOutOfBoundsException();

             }else if (index == size()-1) {

                    add(r);return;     

             }else if (index == 0) {

                    Node n = new Node(r, head);

                    head = n;

             }else {

                    Node temp = head;

                    for(int i = 0; i < index - 1; i++) {

                           temp = temp.getNext();

                    }

                    Node n = new Node(r, temp.getNext());

                    temp.setNext(n);

             }

             size++;

                   

       }

class Node {

            

             private R element;

             private Node next;

            

             public Node(R element, Node next) {

                    this.element = element;

                    this.next = next;

             }

            

            

             public R getElement() {

                    return element;

             }

             public void setElement(R element) {

                    this.element = element;

             }

             public Node getNext() {

                    return next;

             }

             public void setNext(Node next) {

                    this.next = next;

             }           

            

       }

      

      

       class LinkedListIterator implements Iterator {

            

             private Node n;

             private Node bn;

             private Node bbn;

             private boolean removed;

            

             public LinkedListIterator() {

                    n = head;

                    bn = null;

                    bbn = null;

                    removed = false;

             }

             @Override

             public boolean hasNext() {

                    return n != null;

             }

             @Override

             public R next() {

                    if (n == null) {

                           throw new NoSuchElementException();                 

                    }

                    R r = n.element;

                    bbn = bn;

                    bn = n;

                    n = n.next;

                    //n = n.getNext();

                    removed = false;

                    return r;

             }

Answer 1

codes for the implementation of java.util.List

Solution:

Pleas note : As per chegg guidelines, I am allowed to answere first four codes. So here are these methods:

1. public boolean addAll(Collection arg0)

// Java program to illustrate boolean addAll(Collection arg0)
import java.io.*;
import java.util.ArrayList;

public class ArrayListDemo {
   public static void main(String args[])
   {

    ArrayList<Integer> arrlist1 = new ArrayList<Integer>(5);

    arrlist1.add(10);
       arrlist1.add(20);
       arrlist1.add(35);

   System.out.println("Printing list1:");
       for (Integer number : arrlist1)
           System.out.println("Number = " + number);   
       ArrayList<Integer> arrlist2 =
                           new ArrayList<Integer>(5);
       arrlist2.add(26);
       arrlist2.add(32);
       arrlist2.add(31);
       arrlist2.add(38);

       System.out.println("Printing list2:");
       for (Integer number : arrlist2)
           System.out.println("Number = " + number);         

arrlist1.addAll(arrlist2);

       System.out.println("Printing all the elements");

       for (Integer number : arrlist1)
           System.out.println("Number = " + number);         
   }
}

2. public boolean addAll(int arg0, Collection arg1)

// Java program boolean addAll(int arg0, Collection arg1)
import java.io.*;
import java.util.ArrayList;

public class ArrayListDemo {
   public static void main(String args[])
   {
       ArrayList<Integer> arrlist =  new ArrayList<Integer>(5);
       arrlist.add(10);
       arrlist.add(20);
       arrlist.add(30);

       System.out.println("Printing list1:");
       for (Integer number : arrlist)
           System.out.println("Number = " + number);         
       ArrayList<Integer> arrlist2 = new ArrayList<Integer>(5);
       arrlist2.add(40);
       arrlist2.add(70);
       arrlist2.add(81);
       arrlist2.add(35);
       System.out.println("Printing list2:");
       for (Integer number : arrlist2)
           System.out.println("Number = " + number);         

       arrlist.addAll(2, arrlist2);

       System.out.println("Printing all the elements");
       for (Integer number : arrlist)
           System.out.println("Number = " + number);         
   }
}

3. public boolean containsAll(Collection arg0)

// Java code for containsAll() method
import java.util.*;

public class ListDemo {
   public static void main(String args[])
   {
   List<Integer> list = new ArrayList<Integer>();

//add elements into the list
       list.add(10);
       list.add(15);
       list.add(30);
       list.add(20);
       list.add(5);
       System.out.println("List: " + list);

       List<Integer> listTemp = new ArrayList<Integer>();

       listTemp.add(30);
       listTemp.add(15);
       listTemp.add(5);

       System.out.println("Are all the contents equal? " + list.containsAll(listTemp));
   }
}

4. public int lastIndexOf(Object arg0)

// Java code for lastIndexof() method

import java.util.ArrayList;
import java.util.Arrays;
public class ArrayListExample
{
public static void main(String[] args)
{
ArrayList<String> list = new ArrayList<>(Arrays.asList("alex", "brian", "devid","alex","Hennry","gary","alex","harry"));

int lastIndex = list.lastIndexOf("alex");

System.out.println(lastIndex);

lastIndex = list.lastIndexOf("hello");

System.out.println(lastIndex);
}
}

Answer 2

I have given the implementations for the methods. I have just renamed arg0 to obj and index in the method paramater list.

@Override
public int lastIndexOf(Object obj) {
   int i = 0;
   int lastIndex = -1;
   Node temp = head;
   while(temp != null){
       if(temp.getElement().equals(obj)){
           lastIndex = i;
       }
       temp = temp.getNext();
       i++;
   }
   return lastIndex;
}

@Override
public ListIterator<R> listIterator() {
   return new LinkedListIterator();
}

@Override
public ListIterator<R> listIterator(int index) {
   if (index < 0 || index >= size())
       throw new IndexOutOfBoundsException();
   ListIterator<R> iter = listIterator();
   for(int i = 0 ; i < index && iter.hasNext(); i++){
       iter.next();
   }
   return iter;
}