Simple Calculator

import java.util.Scanner;

public class Calculator {
    private double num1;
    private double num2;
    private double result;

    public void getInput() {
        Scanner scanner = new Scanner(System.in);

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

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

    public void add() {
        result = num1 + num2;
        System.out.println("Result: " + result);
    }

    public void subtract() {
        result = num1 - num2;
        System.out.println("Result: " + result);
    }

    public void multiply() {
        result = num1 * num2;
        System.out.println("Result: " + result);
    }

    public void divide() {
        if (num2 != 0) {
            result = num1 / num2;
            System.out.println("Result: " + result);
        } else {
            System.out.println("Error: Division by zero is not allowed.");
        }
    }

    public static void main(String[] args) {
        Calculator calculator = new Calculator();
        calculator.getInput();

        System.out.println("Select an operation:");
        System.out.println("1. Addition");
        System.out.println("2. Subtraction");
        System.out.println("3. Multiplication");
        System.out.println("4. Division");

        Scanner scanner = new Scanner(System.in);
        int choice = scanner.nextInt();

        if (choice == 1) {
            calculator.add();
        } else if (choice == 2) {
            calculator.subtract();
        } else if (choice == 3) {
            calculator.multiply();
        } else if (choice == 4) {
            calculator.divide();
        } else {
            System.out.println("Invalid choice.");
        }
    }
}