My calculator is built with 5 methods:

1. Method for getting the input from the user called getInput (with String argument called prompt)
2. Method for addition (+) called addition (with 2 String arguments called st1 and st2)
3. Method for subtraction (-) called subtraction (with 2 String arguments st1 and st2)
4. Method for multyplyng (*) called multyplyng (with 2 String arguments st1 and st2)
5. Method for division (/) called division (with 2 String arguments st1 and st2)

Here's the code my friend:

import java.util.Scanner;
 
public class Calculator {
    public static void main(String[] args) {
        String s1 = getInput("Enter the 1st number: ");
        String s2 = getInput("Enter the 2nd number: ");
        String operator = getInput("Please choose between + - * and /: ");
 
        double result = 0;
 
        try {
            switch (operator) {
                case "+":
                    result = addition(s1, s2);
                    break;
                case "-":
                    result = subtraction(s1, s2);
                    break;
                case "*":
                    result = multyplyng(s1, s2);
                    break;
                case "/":
                    result = division(s1, s2);
                    break;
                default:
                    System.out.println("There is NO such operation! Please choose between the 4!");
                    break;
            }
            System.out.println("The result is: " + result);
        } catch (Exception e) {
            System.out.println("Number formatting exception " + e.getMessage());
        }
    }
 
    static String getInput(String prompt) {//METHOD FOR GETTING THE INPUT FROM THE USER: getInput (WITH String ARGUMENT prompt)
        System.out.print(prompt);
        Scanner console = new Scanner(System.in);
        return console.nextLine();
    }
 
    static double addition(String st1, String st2) {//METHOD FOR ADDITION: addition (WITH 2 String ARGUMENTS st1 AND st2)
        double d1 = Double.parseDouble(st1);
        double d2 = Double.parseDouble(st2);
        return d1 + d2;
    }
 
    static double subtraction(String st1, String st2) {//METHOD FOR SUBTRACTION: subtraction (WITH 2 String ARGUMENTS st1 AND st2)
        double d1 = Double.parseDouble(st1);
        double d2 = Double.parseDouble(st2);
        return d1 - d2;
    }
 
    static double multyplyng(String st1, String st2) {//METHOD FOR MULTYPLYNG: multyplyng (WITH 2 String ARGUMENTS st1 AND st2)
        double d1 = Double.parseDouble(st1);
        double d2 = Double.parseDouble(st2);
        return d1 * d2;
    }
 
    static double division(String st1, String st2) {//METHOD FOR DIVISION: division (WITH 2 String ARGUMENTS st1 AND st2)
        double d1 = Double.parseDouble(st1);
        double d2 = Double.parseDouble(st2);
        return d1 / d2;
    }
}