Try/catch on switch creating infinite loop on run

Question

I’m also wanting to implement a try/catch within the while so that when a user enters a double with a dot instead of a comma, the program points the error and sends it back to code execution.

But when testing the error, the program enters a loop infinity, just putting a break the program stops running, but wanted to know if there is a possibility to return the execution of the program without having to run it again.

import java.util.InputMismatchException;
import java.util.Scanner;

public class Teste_Calc extends Calculadora {

    public static void main(String[] args)  {

        Calculadora c = new Calculadora();
        Scanner sc1 = new Scanner(System.in);
        double n1,n2;
        double resultado;
        int opcao;
        boolean x=true;

        while(x) {
            try {
            System.out.println("---------------------------------");
            System.out.println("Escolha uma das opções a seguir:");
            System.out.println("1) Somar!");
            System.out.println("2) Subtrair!");
            System.out.println("3) Multiplicar!");
            System.out.println("4) dividir!");
            System.out.println("5) Sair do programa!");
            System.out.println("---------------------------------");


            opcao = sc1.nextInt();


        if (opcao == 5) {
            System.out.println("Programa finalizado!");
            break;
        }

        else{

            switch(opcao) {


            case 1:

                System.out.println("Insita o valor do numero 1:");
            n1 = sc1.nextDouble();
                System.out.println("Insira o valor do numero 2:");
            n2 = sc1.nextDouble();
            resultado = c.somar(n1,n2);
            System.out.println("O resultado é: "+ resultado);

            break;

            case 2:
                System.out.println("Insita o valor do numero 1:");
                n1 = sc1.nextDouble();
                    System.out.println("Insira o valor do numero 2:");
                n2 = sc1.nextDouble();
                resultado = c.subtrair(n1,n2);
                System.out.println("O resultado é: "+ resultado);
                break;

            case 3:
                System.out.println("Insita o valor do numero 1:");
                n1 = sc1.nextDouble();
                    System.out.println("Insira o valor do numero 2:");
                n2 = sc1.nextDouble();
                resultado = c.Multiplicar(n1,n2);
                System.out.println("O resultado é: "+ resultado);
                break;

            case 4:
                System.out.println("Insita o valor do numero 1:");
                n1 = sc1.nextDouble();
                    System.out.println("Insira o valor do numero 2:");
                n2 = sc1.nextDouble();
                resultado = c.dividir(n1,n2);
                System.out.println("O resultado é: "+ resultado);
                break;  

                default:
                    System.out.println("Opção invalida");

            }

     }
            }

            catch(InputMismatchException exception) {
                System.out.println("Caracter inserido não compatível!" );
                 continue;
            }
        }       
    }
}

Answer 1

The code is confusing and so it is even difficult to find the error, and easy to make it. It’s too big a method with too much code repetition, but I’m not gonna try to fix it. At least keep things closer, keep the buildings smaller, don’t need to have a try so great. Actually I’m critical of the use of exception for this kind of thing, but then it’s a Java API error and you can do little (it might, but it’s too much work), so you have to deal with this problem. I took a few pieces to compile since I don’t have them, but this legacy seems very wrong too, even though it works. See how it gets simpler (I don’t even know where the bug was, I just organized and it worked):

import java.util.InputMismatchException;
import java.util.Scanner;

class Teste_Calc {
    public static void main(String[] args)  {
        while (true) {
            System.out.println("---------------------------------");
            System.out.println("Escolha uma das opções a seguir:");
            System.out.println("1) Somar!");
            System.out.println("2) Subtrair!");
            System.out.println("3) Multiplicar!");
            System.out.println("4) dividir!");
            System.out.println("5) Sair do programa!");
            System.out.println("---------------------------------");
            int opcao;
            try {
                Scanner sc1 = new Scanner(System.in);
                opcao = sc1.nextInt();
            } catch (InputMismatchException exception) {
                System.out.println("Caracter inserido não compatível!");
                continue;
            }
            if (opcao == 5) {
                System.out.println("Programa finalizado!");
                break;
            } else {
                switch (opcao) {
                case 1:
                    System.out.println("1) Somar!");
                    break;
                case 2:
                    System.out.println("2) Subtrair!");
                    break;
                case 3:
                    System.out.println("3) Multiplicar!");
                    break;
                case 4:
                    System.out.println("4) dividir!");
                    break;  
                default:
                    System.out.println("Opção invalida");
                }
            }
        }       
    }
}

I put in the Github for future reference.

Note how everything I do is closer to where it is used, including variable declaration.