Question

Consider the following class definition:

                  public class Parent {

              private int varA;

              protected double varB;

              public Parent(int a, double b){

varA = a;

varB = b;

              }

              public int sum( ){

                   return varA + varB;

              }

public String toString( ){

                   return "" + varA + "   " + varB;

              }

        }

Consider that you want to extend Parent to Child. Child will have a third int instance data varC.

1. Write the parameterized constructor definition for Child;
2. Write the code to override the sum() method to now add all three values and return the sum;
3. Write the code to define a method average() to calculate and return the average of varB and varC.
4. Write the code to override the toString() method for Child.

Answer 1

code:

public class Main
{
   public static void main(String[] args) {
  
   System.out.println("Parent class");
       Parent ob = new Parent(3,4.5);
       System.out.println(ob);
       System.out.println("Sum is: "+ob.sum());
      
       System.out.println("\nChild class");
       Child ob1 = new Child(3,4,5);
       System.out.println(ob1);
       System.out.println("Sum is: "+ob1.sum());
       System.out.println("Average is: "+ob1.average());
   }
}

class Parent {
private int varA;
protected double varB;
public Parent(int a, double b)
{
varA = a;
varB = b;
}
  
// If we add double and int it will always returns double not int. So i have changed this
public double sum( )
{
return varA+varB;
}

public String toString( )
{
return "" + varA + " " + varB;
}
}

// Creating child class which extends parent class
class Child extends Parent
{
private int varC; // third instance
  
// We cant access private variables of parent class in child class.
// The private variables are only accessed by that class methods
  
// parameterized constructor for child class
public Child(int a,double b,int c)
{
// calling super/parent class constructor
super(a,b);
varC = c;
}
  
// Override sum method
public double sum( )
{
return super.sum()+varC;
}
  
// Creating method average
public double average()
{
return (super.varB+varC)/2;
}
  
// Override method toString
public String toString( )
{
return super.toString()+ " " + varC;
}
}

OUTPUT: