cannot find symbol (calculator)

Question

I recently made a program to be a calculator but three errors occurred. Here is the code:

import java.util.Scanner;
public class mathyStuff {
    public static void main(String[] args) throws InterruptedException {
        Scanner raw = new Scanner(System.in);
        String input = raw.nextLine();
        int y = 0;
        while (y < input.length()) {
            if (input.substring(y, y+1) == "+" || input.
            substring(y, y+1) == "-" ||  input.substring(y, y+1) == "/" ||  input.substring(y, y+1) == "*") {
                String x = input.substring(y, y+1);
                int z1 = Integer.parseInt(input.substring(0,y));
                int z2 = Integer.parseInt(input.substring(y+1, 0));
            }
            else {
                y = y + 1;
            }
        }
        math(z1,x,z2);
    }
    public static void math (int num1, String op, int num2) throws InterruptedException {
        if (op == "+") {
            System.out.println(String.valueOf(num1 + num2));
        }
        if (op == "-") {
            System.out.println(String.valueOf(num1 - num2));
        }
        if (op == "*") {
            System.out.println(String.valueOf(num1 * num2));
        }
        if (op == "/") {
            System.out.println(String.valueOf(num1 / num2));
        }
    }
}

Here is the errors:

Compilation Errors Detected

Line: 18
cannot find symbol
  symbol:   variable z1
  location: class mathyStuff

Line: 18
cannot find symbol
  symbol:   variable x
  location: class mathyStuff

Line: 18
cannot find symbol
  symbol:   variable z2
  location: class mathyStuff

I'm currently using a website called browxy, an online java compiler. And yes, I know. Download eclipse. I can't bring my computer everywhere I go so I use this instead.

Beside problem with scope you should also correct way you [compare strings](http://stackoverflow.com/questions/513832/how-do-i-compare-strings-in-java) — Pshemo, May 06 '15 at 22:09
Yours is a scope problem. Your variables are only visible within the scope that they've been declared in. — Hovercraft Full Of Eels, May 06 '15 at 22:09

score 1 · Answer 1 · answered May 06 '15 at 22:09

1

This is a scope issue.

You can't access x, z1 and z2 because they're declared inside a while loop, but you're trying to access them outside the while loop.

You probably want to move the math function call inside the if block inside the while loop.

answered May 06 '15 at 22:09

Aify

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I already edited my answer for that 10 minutes ago - move the math(z1, x, z2) call inside the if block that's inside the while loop. – Aify May 06 '15 at 22:21

Patrick vD · Answer 2 · 2015-05-06T22:33:57.293

You are essentially asking for a variable in a situation where java can't confirm that the variable has been defined. You need to pre-define the variable in a location outside any while loops or if loops that end before the calling of these variables.
Try adding this right before the int y = 0;:
int z1 = 0; int z2 = 0;
Also, where do you define x? If you mean the string x, you need to write "x" on line 18. If you mean a variable named x, make sure it is defined in the right scope. As it is, I can't find it anywhere.

Side note: your math method can't take "x" as an input for the second variable. It only takes "+", "-", "*", and "/". If you want to be able to use "x", you will need to change your math method.

cannot find symbol (calculator)

2 Answers2