UserInterface.java

import java.util.InputMismatchException;
import java.util.Scanner;

public class UserInterface {
    private Scanner scanner;
    private Calculator calculator;

    public UserInterface() {
        scanner = new Scanner(System.in);
        calculator = new Calculator();
    }

    public void performAddition() {
        System.out.println("Enter how many numbers you want to add (2 or 3): ");
        int count = scanner.nextInt();

        if (count == 2) {
            System.out.print("Enter first number: ");
            double a = scanner.nextDouble();
            System.out.print("Enter second number: ");
            double b = scanner.nextDouble();
            double result = calculator.add(a, b);
            System.out.println("Result: " + result);
        } else if (count == 3) {
            System.out.print("Enter first number: ");
            int a = scanner.nextInt();
            System.out.print("Enter second number: ");
            int b = scanner.nextInt();
            System.out.print("Enter third number: ");
            int c = scanner.nextInt();
            int result = calculator.add(a, b, c);
            System.out.println("Result: " + result);
        } else {
            System.out.println("Invalid input! Only 2 or 3 numbers allowed.");
        }
    }

    public void performSubtraction() {
        System.out.print("Enter first integer: ");
        int a = scanner.nextInt();
        System.out.print("Enter second integer: ");
        int b = scanner.nextInt();
        System.out.println("Result: " + calculator.subtract(a, b));
    }

    public void performMultiplication() {
        System.out.print("Enter first double: ");
        double a = scanner.nextDouble();
        System.out.print("Enter second double: ");
        double b = scanner.nextDouble();
        System.out.println("Result: " + calculator.multiply(a, b));
    }

    public void performDivision() {
        try {
            System.out.print("Enter numerator: ");
            int a = scanner.nextInt();
            System.out.print("Enter denominator: ");
            int b = scanner.nextInt();
            double result = calculator.divide(a, b);
            System.out.println("Result: " + result);
        } catch (ArithmeticException e) {
            System.out.println(e.getMessage());
        }
    }

    public void mainMenu() {
        int choice;
        do {
            System.out.println("\nWelcome to the Calculator Application!");
            System.out.println("1. Add Numbers");
            System.out.println("2. Subtract Numbers");
            System.out.println("3. Multiply Numbers");
            System.out.println("4. Divide Numbers");
            System.out.println("5. Exit");
            System.out.print("Enter your choice: ");
            try {
                choice = scanner.nextInt();
                switch (choice) {
                    case 1: performAddition(); break;
                    case 2: performSubtraction(); break;
                    case 3: performMultiplication(); break;
                    case 4: performDivision(); break;
                    case 5: System.out.println("Exiting... Thank you!"); break;
                    default: System.out.println("Invalid choice. Try again!");
                }
            } catch (InputMismatchException e) {
                System.out.println("Invalid input! Please enter a number.");
                scanner.next(); // clear invalid input
                choice = 0;
            }
        } while (choice != 5);
    }

    public static void main(String[] args) {
        UserInterface ui = new UserInterface();
        ui.mainMenu();
    }
}