Rewrite the Course class in Listing 10.6 to implement the comparable and the clo

Question

Rewrite the Course class in Listing 10.6 to implement the comparable and the cloneable
interfaces. The clone method must allow a deep copy on the students field. In addition, add the
equals(Object o) and the toString() methods.
Write a test program to invoke the compareTo, clone, equals, and toString methods in a meaningful way.

Below is the Listing from the book that needs to be rewritten

public class Course {
   private String courseName;
   private String[] students = new String[100];
   private int numberOfStudents;

   public Course(String courseName) {
       this.setCourseName(courseName);
   }

   public void addStudent(String student) {
       students[numberOfStudents] = student;
       numberOfStudents++;
   }

   public String[] getStudents() {
       return students;
   }

   public int getNumberOfStudents() {
       return numberOfStudents;
   }

   public void dropStudent(String student) {
   }

   public String getCourseName() {
       return courseName;
   }
}

Explanation / Answer

import java.util.Arrays;

public class Course implements Cloneable, Comparable<Course>{
   private String courseName;
   private String[] students = new String[100];
   private int numberOfStudents;

   public Course(String courseName) {
       this.setCourseName(courseName);
   }

   public void addStudent(String student) {
       students[numberOfStudents] = student;
       numberOfStudents++;
   }

   public String[] getStudents() {
       return students;
   }

   public int getNumberOfStudents() {
       return numberOfStudents;
   }

   public void dropStudent(String student) {
   }

   public String getCourseName() {
       return courseName;
   }

   public void setCourseName(String course){
       courseName = course;
   }

   @Override
   public int compareTo(Course o) {
       // comparing based on course name
       return this.courseName.compareToIgnoreCase(o.courseName);
   }
   @Override
   public Course clone() {
       Course p;
       p = new Course(courseName);
       p.students = Arrays.copyOf(students, students.length);
       p.numberOfStudents = numberOfStudents;
       return p;
   }
  
   @Override
   public boolean equals(Object obj) {
       Course c = (Course)obj;
       return courseName.equalsIgnoreCase(c.courseName);
   }
  
   @Override
   public String toString() {
       return "Course[ Name: "+courseName+" Students Number: "+numberOfStudents+" "+studentsName()+" ]";
   }
  
   private String studentsName(){
       StringBuffer bf = new StringBuffer();
       for(int i=0; i<numberOfStudents; i++){
           bf.append(students[i]+" ");
       }
       return bf.toString();
   }
}

// Test class

public class CourseTest {

   public static void doSelectionSort(Course[] arr){

       for (int i = 0; i < arr.length - 1; i++)
       {
           int index = i;
           for (int j = i + 1; j < arr.length; j++)
               if (arr[j].compareTo(arr[index]) < 0)
                   index = j;

           Course smaller = arr[index];
           arr[index] = arr[i];
           arr[i] = smaller;
       }
   }
   public static void main(String[] args) {
       Course c1 = new Course("Computer");

       // adding students
       c1.addStudent("Pinki");
       c1.addStudent("Mukesh");
       c1.addStudent("Alex");
       c1.addStudent("Flex");
       c1.addStudent("Bob");
       // calling toString method
       System.out.println(c1.toString());
       System.out.println();
       // cloning course c1
       Course clone = c1.clone();
       // calling to string on clone
       System.out.println(clone.toString());

       System.out.println();

       // comparing clone and c1

       System.out.println("Is c1 and clone equal ? : "+clone.equals(c1));
       System.out.println();
       // creating course array
       Course[] courses = {
               c1, clone, new Course("Electrical"), new Course("Automation"), new Course("Programming")};

       // printing before sorting
       for(Course c : courses){
           System.out.print(c.getCourseName()+" ");
       }
       System.out.println(" ");
       // sorting c1 , using compare method
       doSelectionSort(courses);

       // printing after sorting
       for(Course c : courses){
           System.out.print(c.getCourseName()+" ");
       }
   }
}

/*

Output:

Course[ Name: Computer
Students Number: 5
Pinki Mukesh Alex Flex Bob
]

Course[ Name: Computer
Students Number: 5
Pinki Mukesh Alex Flex Bob
]

Is c1 and clone equal ? : true

Computer Computer Electrical Automation Programming

Automation Computer Computer Electrical Programming

*/

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