Question

Modify the following java code, utilizing a loop mechanism to enable the user to use the calculator more than once.
The program does the following:
   It prompts the user to enter 2 numbers.
   It prompts the user to choose an operation to perform on those numbers:
   Operation 1: Addition.
   Operation 2: Subtraction.
   Operation 3: Multiplication.
   Operation 4: Division.
   It outputs the result of the operation.
   It asks the user if they want to perform another calculation, using “-1" as a stop value.

The code:

package udh;
import java.util.Scanner;
public class Udh {

public static void main(String[] args) {
Scanner input = new Scanner(System.in);
  

System.out.println("Enter two numbers");
int num1 = input.nextInt();
int num2 = input.nextInt();

System.out.println("Choose the operator; *, /, +, - ");
char choice = input.next().charAt(0);
switch (choice)
{
case '+':
int add= num1+num2;
System.out.println(add);
break;

case '-':
int sub = num1-num2;
System.out.println(sub);
break;

case '*':
int mul= num1*num2;
System.out.println(mul);
break;

case '/':
double div= num1/num2;
System.out.println(div);
break;

default :
System.out.println("Invalid operator");
}
  

}
}

Answer 1

To enable the user to do multiple calculations we use do-while loop. We take a variable "next" and if the user does not wants to calculate further, then next = -1.

The code is as follows:

package udh;

import java.util.Scanner;
public class Udh {

public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        int next; //next variable decides whether to calculate more based on user choice
        do{
                System.out.println("Enter two numbers");
                int num1 = input.nextInt();
                int num2 = input.nextInt();
                
                System.out.println("Choose the operator; *, /, +, - ");
                char choice = input.next().charAt(0);
                switch (choice){
                        case '+':
                        int add= num1+num2;
                        System.out.println(add);
                        break;
                        
                        case '-':
                        int sub = num1-num2;
                        System.out.println(sub);
                        break;
                        
                        case '*':
                        int mul= num1*num2;
                        System.out.println(mul);
                        break;
                        
                        case '/':
                        double div= (double)num1/num2;
                        System.out.println(div);
                        break;
                        
                        default :
                        System.out.println("Invalid operator");
                }
                        //Taking input for stopping
                        System.out.println("Another calculation? (Type -1 to stop)");
                        next = input.nextInt(); //Assignment of value to next
        }while(next!=-1); //Do while loop for multiple calculations. It iterates if next is not -1
        System.out.println("Bye Bye!!");
        input.close();
}
}

Output:

Hope this helps
If you have any doubt feel free to comment
Thank You!!