Having troubles with a simple calculator I've been trying to make

Question

I've been constantly getting these errors for a simple calculator I've been trying to make Information:java: Errors occurred while compiling module 'Learning'

Error:(24, 31) java: bad operand types for binary operator '*'
 first type:  java.util.Scanner
  second type: java.util.Scanner


Error:(27, 31) java: bad operand types for binary operator '/'
first type:  java.util.Scanner
second type: java.util.Scanner


 Error:(21, 31) java: bad operand types for binary operator '-'
 first type:  java.util.Scanner
 second type: java.util.Scanner


Error:(18, 31) java: bad operand types for binary operator '+'
 first type:  java.util.Scanner
  second type: java.util.Scanner


Error:(16, 16) java: incompatible types: java.util.Scanner cannot be converted to int

This is my code

import java.util.Scanner;

class Main {

public static void main(String[] args) {
    Scanner Operation = new Scanner(System.in);
    Scanner num1 = new Scanner(System.in);
    Scanner num2 = new Scanner(System.in);
    float result = 0;

    System.out.println("What is your first number?");
    int num1int = num1.nextInt();
    System.out.println("What is your second number?");
    int num2int = num2.nextInt();
    System.out.println("What operation would you like to perform?");
    switch (Operation) {
        case "addition":
            result = num1 + num2;
            break;
        case "subtraction":
            result = num1 - num2;
            break;
        case "multiplication":
            result = num1 * num2;
            break;
        case "division":
            result = num1 / num2;
            break;
    }

}

Thanks for your help guys, also, sorry if i'm not supposed to be posting this, I'm new.

Answer 1

num1 and num2 are not numbers, but of type java.util.Scanner .

Probably you would to use num1int and num2int , as follow:

 switch (Operation) {
    case "addition":
        result = num1int + num2int;
        break;
    case "subtraction":
        result = num1int - num2int;
        break;
    case "multiplication":
        result = num1int * num2int;
        break;
    case "division":
        result = num1int / num2int;
        break;
}

I suggest to change the names to reflect the real types as follow:

Scanner scannerNum1 = new Scanner(System.in);
Scanner scannerNum2 = new Scanner(System.in);
float result = 0;

System.out.println("What is your first number?");
int num1 = scannerNum1.nextInt();
System.out.println("What is your second number?");
int num2 = scannerNum2.nextInt();
switch (Operation) {
    case "addition":
        result = num1 + num2;
        break;
    case "subtraction":
        result = num1 - num2;
        break;
    case "multiplication":
        result = num1 * num2;
        break;
    case "division":
        result = num1 / num2;
        break;
}

Note: additionally is not necessary to define two scanners. One is enough.

Answer 2

In your code, you have the line

result = num1 + num2;

where you try to add num1 and num2 together. Given the variable names, this seems reasonable, but when you consider these lines, it becomes ridiculous:

Scanner num1 = new Scanner(System.in);
Scanner num2 = new Scanner(System.in);

You can't add two scanners, that doesn't make sense in theory, and it makes even less sense in practice. I assume that you were trying to do this:

result = num1int + num2int;

This is fine in theory, but when you try do do this operation with num1int = 3 and num2int = 4, you'll get result = 0 instead of result = .75:

result = num1int / num2int;

This is because of integer division, which always rounds towards 0. Put a cast to double to avoid this, like so:

result = ((double) num1int) / num2int;

I hope this helped to clarify your problem. Good luck!