Question

I have an issue with accessing variables initialized in a switch-statement, and then using them outside switch.

This is what my code should produce:
What is: X (+-* or /) X

Here’s my Java code:

import java.util.Random;
import java.util.Scanner;

public class Test2 {
        public static void main(String[]args){

        Random rand = new Random();
        Scanner sc = new Scanner(System.in);

        int svar, ans;
        int tal1 = rand.nextInt(100) + 1;
        int tal2 = rand.nextInt(100) + 1;

        String characters = "+-*/";
        int r = rand.nextInt(characters.length());
        char randomChar = characters.charAt(r);

        switch(randomChar){
        case '+':
            ans = tal1 + tal2;
            break;
        case '-':
            ans = tal1 - tal2;
            break;
        case '*':
            ans = tal1 * tal2;
            break;
        case '/':
            ans = tal1 / tal2;
            break;
        }

        System.out.println("What is: "+tal1+randomChar+tal2+"?");
        svar = sc.nextInt();

        if (svar == ans)
            System.out.println("Correct!");
        else
            System.out.println("Wrong - Right answer: "+ans);

        }
}

As you can see, “ans” has been declared and initialized. However, I want to utilize the ans variable in both the if statement (in order to compare the result) and the output.

Now I could expand each case and write both the if statements and the outputs, but the code would be too exessive as I’m trying to do a similar code, but smaller. Any tips how this work would work?

Here’s the compilation error I get:

Exception in thread "main" java.lang.Error: Unresolved compilation problems: 
    The local variable ans may not have been initialized
    The local variable ans may not have been initialized

    at Test2.main(Test2.java:36)

Answer 1

Add a default case to catch any input that isn’t recognized. In your case, this could throw a RuntimeException, since something is wrong with your code if this case is reached.

default: 
  throw new RuntimeException("Unexpected operation: " + randomChar);

The error you are getting means that there is a code path that fails to initialize ans. Do not take the easy way out and initialize ans with a meaningless value when it is declared! That will just hide this valuable warning about a real problem with your code.