Calculator.java

import java.util.Scanner;

public class Calculator {
    public static double add(double a, double b) {
        return a + b;
    }

    public static double subtract(double a, double b) {
        return a - b;
    }

    public static double multiply(double a, double b) {
        return a * b;
    }

    public static double divide(double a, double b) {
        if (b == 0) {
            System.out.println("Error: Division by zero.");
            return Double.NaN;
        }
        return a / b;
    }

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        boolean running = true;

        while (running) {
            System.out.println("Choose operation: (+, -, *, /) ");
            String op = scanner.next();

            

            System.out.print("Enter first number: ");
            double num1 = scanner.nextDouble();

            System.out.print("Enter second number: ");
            double num2 = scanner.nextDouble();

            double result = 0;
            switch (op) {
                case "+":
                    result = add(num1, num2);
                    break;
                case "-":
                    result = subtract(num1, num2);
                    break;
                case "*":
                    result = multiply(num1, num2);
                    break;
                case "/":
                    result = divide(num1, num2);
                    break;
                default:
                    System.out.println("Invalid operation.");
                    continue;
            }
            System.out.println("Result: " + result);
        }

        scanner.close();
        System.out.println("");
    }
}