How to use try-catch in Java? - exception

Question

I am trying to learn try and catch block but with below code something is missing, and my code is not giving my custom error given in catch block. What is the problem here?
Here is my code :
package com.example.java;
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
int num1;
int num2;
String operatorValue;
System.out.println("Please Enter First Number :");
Scanner firstInput = new Scanner(System.in);
num1 = firstInput.nextInt();
System.out.println("Please Enter Second Number :");
Scanner secondInput = new Scanner(System.in);
num2 = secondInput.nextInt();
System.out.println("Please Select operation + - * / % :");
Scanner operatorInput = new Scanner(System.in);
operatorValue = operatorInput.nextLine();
double results = 0;
try {
switch (operatorValue) {
case "+":
results = num1 + num2;
break;
case "-":
results = num1 - num2;
break;
case "*":
results = num1 * num2;
break;
case "/":
results = num1 / num2;
break;
case "%":
results = num1 % num2;
break;
default:
System.out.println("please Enter a valid operator value");
return;
}System.out.println("The Result is :"+ results);
} catch (Exception e) {
System.out.println("please enter a valid number "+ e.getMessage());
}
}
}

Answer 1

Your try...catch block doesn't include the input part. This is the part that is problematic so wrap it instead of the calculation:
int num1;
int num2;
String operatorValue;
try {
System.out.println("Please Enter First Number :");
Scanner firstInput = new Scanner(System.in);
num1 = firstInput.nextInt(); // can produce error
System.out.println("Please Enter Second Number :");
Scanner secondInput = new Scanner(System.in);
num2 = secondInput.nextInt(); // can produce error
System.out.println("Please Select operation + - * / % :");
Scanner operatorInput = new Scanner(System.in);
operatorValue = operatorInput.nextLine();
} catch (Exception e) {
System.out.println("please enter a valid number "+ e.getMessage());
}
// Rest of code