Question

Hello,

Please write this program in java and include a lot of comments and please try to make it as simple/descriptive as possible since I am also learning how to code. The instructions the professor gave was:

Create your own class

• Your own class can be anything you want

• Must have 3 instance variables

• 1 constructor variable → set the instance variables

• 1 method that does something useful in relation to the class

• Create a driver class that creates an object ( the object is referred to the method above)

• Call the method that I created using the object

An example she gave was using like a student class because it has many variables such as grades, classification, major, etc.

Answer 1

Implementation In JAVA:

import java.util.ArrayList;
import java.util.Scanner;

//Driver class
public class Student_Driver {

//   main method or driver method
   public static void main(String[] args) {
      
//       list consists of Students
       ArrayList<Students> list= new ArrayList<Students>();
      
//   create instance of Scanner class for taking inputs from users  
       Scanner s= new Scanner(System.in);
      
       System.out.println("Enter the Details of 5 Students of class");
      
       System.out.println();
      
//       take details of 5 students so looping untill 5
       for(int i=0;i<5;i++) {
          
           System.out.println("Enter the details of "+(i+1)+"th Student : ");
          
//           take details from user as input
           System.out.print("Enter the Name of Student : ");
           String name=s.next();
          
           System.out.print("Enter the Roll no of Student : ");
           int roll=s.nextInt();
          
           System.out.print("Enter the Grade of Student : ");
           double grade=s.nextDouble();
          
//           create instance of Students class and pass arguments
//           in Constructor of Students class
           Students st= new Students(name,roll,grade);
          
//           add instance of Students class in List for future refrence
           list.add(st);
          
           System.out.println();
          
       }
      
//       showing details of Students
       System.out.println("Student of whole class with details : ");
      
//       will print details of Students
       for(int i=0;i<list.size();i++) {
          
//           Store instance/object of Student class and
           Students st = list.get(i);
//           and call the function in Students class for printing details
           st.to_String();
           System.out.println();
          
       }
      
System.out.println();
  
// will call the function average_grades_of_whole_class from driver class
System.out.println("The Average grades of whole class is "+average_grades_of_whole_class(list));
      
      
   }
  
//   made static because directly access into main
   public static double average_grades_of_whole_class(ArrayList<Students> list) {
      
//       will store sum of all grades
       double sum=0;
      
//       loop untill list.size
       for(int i=0;i<list.size();i++) {
          
           Students st = list.get(i);
//           call getgrade for every student and store in sum
           sum+=st.getgrade();
          
       }
//       getting average
       double avg=sum/list.size();
      
//       return avg.
       return avg;
   }

}

// class Student
class Students{
  
//   Instance variables declared private so
//   no one from outside access them
   private String name;
   private int roll_no;
   private double grade;
  
//   3 argument constructor
   public Students(String name,int roll_no,double grade) {
      
//       initialize variables
       this.name=name;
       this.roll_no=roll_no;
       this.grade=grade;
      
   }
  
//   now below are getters and setters through which we can access those variables
  
//   will return name
   public String getname() {
      
       return name;
   }
  
//   will set name
public void setname(String name) {
      
       this.name= name;
   }
  
// will return roll.no
public int getroll() {
  
   return roll_no;
}
  
// will set roll no.
public void setroll(int roll_no) {
       this.roll_no=roll_no;
   }
  
// will return grade
public double getgrade() {
   return grade;
}
  
// will set grades
   public void setgrades(double grade) {
      
       this.grade=grade;
      
   }
  
  
//   method that does something useful in relation to the class
//   this will print the details of Student
  
   public void to_String() {
      
       System.out.println("Name : "+name );
       System.out.println("Roll no. : "+roll_no );
       System.out.println("Grade : "+grade );
      
   }

  
}

SAMPLE OUTPUT:

If you have any doubt regarding this question please ask mein comments

// THANK YOU:-)