آلة حاسبة بسيطة بلغة Java باستخدام switch وScanner

import java.util.Locale;
import java.util.Scanner;

public class Calculator {
    public static void main(String[] args) {
        try (Scanner input = new Scanner(System.in)) {
            input.useLocale(Locale.US);
            System.out.println("Enter the first number, then the second number:");
            if (!input.hasNextDouble()) {
                System.out.println("Invalid first number.");
                return;
            }
            double first = input.nextDouble();
            if (!input.hasNextDouble()) {
                System.out.println("Invalid second number.");
                return;
            }
            double second = input.nextDouble();
            if (!Double.isFinite(first) || !Double.isFinite(second)) {
                System.out.println("Use finite numbers only.");
                return;
            }
            System.out.println("Enter an operator: + - * /");
            if (!input.hasNext()) return;
            String operator = input.next();
            double result;
            switch (operator) {
                case "+": result = first + second; break;
                case "-": result = first - second; break;
                case "*": result = first * second; break;
                case "/":
                    if (second == 0.0) {
                        System.out.println("Cannot divide by zero.");
                        return;
                    }
                    result = first / second;
                    break;
                default:
                    System.out.println("Unknown operator.");
                    return;
            }
            if (!Double.isFinite(result)) {
                System.out.println("Result is outside the supported range.");
                return;
            }
            System.out.println(first + " " + operator + " " + second + " = " + result);
        }
    }
}