Question

I used this code for an easy if/ else statement that will sum the answer if x was greater than y, and will subtract it if x was not greater than y ! For some reason I’m getting a run time error.

Can anyone help me with this?
The code is :

import java.util.Scanner;

public class calculation
{
    public static void main(String[] args)
    {      
        int x,y,answer;

        Scanner kb = new Scanner(System.in);
        System.out.println(" Enter x & Y " );

        x = kb.nextInt();
        y = kb.nextInt();

        if (x > y) {    
            answer = (x + y);
        }  
        else if (x < y) {
            answer=(x-y);
        }

    }
}

This is the message I get : Warning: The local variable answer is never read

Answer 1

If the error you’re getting is something like this:

Foo.java:23: error: variable answer might not have been initialized
        System.out.print("answer is " + Integer.toString(answer));

then the problem is that answer might not have had any value set, and the computer gives up and prints an error message instead of possibly returning garbage.

How can answer not have a value set? You set answer to x+y if x>y, and if x<y you set answer=x-y; but what if x=y? There’s nothing that tells the computer what to do in that case. Even though x might not be equal to y for the particular inputs you typed into your program, Java gives you an error message now in the hopes that you would rather get an error now, when it can easily be fixed, than sometime much later when someone first inputs equal values of x and y.

You can fix this by changing x>y to x>=y, or x<y to x<=y, or by adding a third x==y case.

---

If the warning you are getting is

Warning: The local variable answer is never read

Then you need to add a statement that uses answer in some way, for example by adding this at the end of the method:

System.out.print("answer is " + Integer.toString(answer));

However, note that this is just a warning, not an error, so even though the message pops up, it should run just fine—try it! Of course, you won’t be able to see what value answer gets, because, as the warning says, answer is never read in the current code.