Question

In this next example, we'll build two classes that implement the Cloneable Interface. The QuizTracker class contains an ArrayList of QuizScore objects, and it's up to us to build these two classes so that we can make deep copies of QuizTrackers (and share no internal aliases). The key idea here is that to make deep copies of compound objects (or lists of objects), we need to copy (using clone) every object in every list, and even make copies of the list objects (ArrayLists here) themselves. (1) Start by building a small QuizScore Class that contains only one data item: an int that corresponds to the score received on the quiz. (2) Build a second class, QuizTracker, that contains an ArrayList of QuizScore objects (Array List < QuizScore > ) as its only data item a. This is just like an IntList covered previously, but instead of ints well be storing QuizScore and instead of arrays we can use an ArrayList here. (3) Add getters and setters to QuizScore for the score, and provide an add(QuizScore) method for class QuizTracker (4)Implement the cloneable interface for the QuizScore class (5) Implement the cloneable interface for the QuizTracker class, as well a. This should not use ArrayList. Clone(), as this is a shallow copy. B. Instead, to create a copy of QuizTracker, you must first build a newly created ArrayList in (b) c. In this way, if we, make a copy of the container (ArrayList), and all the contents in the container (QuizScores), weve succeeded in producing a deep copy for the QuizTracker class.

Answer 1

Following code is for the Quizscore class. Comments are added at places to explain the process performed.

public class Quizscore implements Cloneable{ //Task 4
   int item; //Task 1
   public int getItem() { // Task 3
       return item;
   }

   public void setItem(int item) {// Task 3
       this.item = item;
   }
  
  
/* The below method is custom made to call the super.clone() method for cloning to take place
   Also clone() is a protected method that it is accessible for all subclasses of particular class.
    So to enable the Quiztracker class to use clone() this custom made method getClone() is created.
it just calls the super.clone() from within and return the cloned value to the caller method.*/
   public Quizscore getClone(){
       try {
           return (Quizscore) super.clone();
       } catch (CloneNotSupportedException e) {
           // TODO Auto-generated catch block
           e.printStackTrace();
       }
       return this;
    }

}

Following code is for the Quiztracker class. Comments are added at places to explain the process performed.

import java.util.ArrayList;

public class Quiztracker implements Cloneable{ ////Task 5
   ArrayList<Quizscore> qtracker; // Task 2
   ArrayList<Quizscore> copy_qtracker; // Task 5b
  
   Quiztracker(){
       qtracker=new ArrayList<Quizscore>();
       copy_qtracker=new ArrayList<Quizscore>();
   }
  
   //Task 3
   public void add(Quizscore score){ //Taking in cloned items of Quizscore object
      
       qtracker.add(score);
       copy_qtracker.add(score.getClone()); //Task 5c
   /*Storing items of Cloned Quizscore object to new ArrayList copy_qtracker by calling the
   custom made getClone() method defined in Quizscore class*/
   }

   //The below 2 methods are created to traverse through the MainList qtracker and
   //the Cloned list copy_qtracker

   public void getMainList() {
       // TODO Auto-generated method stub
      
       for(int i=0;i<qtracker.size();i++){
           System.out.print(qtracker.get(i).getItem()+" ");
       }
   }

   public void getCloneList() {
       // TODO Auto-generated method stub
       for(int i=0;i<qtracker.size();i++){
           System.out.print(copy_qtracker.get(i).getItem()+" ");
       }
   }
  
}

Finally below is the Main Class that is created to test the functionalities of the above 2 classes.

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

//Creating 3 Quizscore objects for storage and 1 Quiztracker object
       Quizscore sscore=new Quizscore();
       Quizscore sscore1=new Quizscore();
       Quizscore sscore2=new Quizscore();
       Quiztracker trac=new Quiztracker();
      

        sscore.setItem(381);     
       sscore1.setItem(8481);
       sscore2.setItem(919);
      
       trac.add(sscore);
       trac.add(sscore1);
       trac.add(sscore2);
      
      
       System.out.println("Original List Items");
       trac.getMainList();
      
      
       System.out.println("\nCloned List Items");
       trac.getCloneList();
   }

}

This is the output that is generated in the test run of the Main class