BankApp.java

import java.io.IOException;
import java.util.Scanner;

/**
 * The BankApp class is the driver for the banking application.
 * It lets the user create accounts (NewAccount) and deposit/withdraw (AccessAccount).
 * The logged-in account is held in an Account variable, so Java picks AccessAccount's
 * overriding deposit()/withdraw() at runtime (polymorphism / dynamic dispatch).
 */
public class BankApp {
    public static void main(String[] args) throws IOException {
        Scanner in = new Scanner(System.in);
        boolean running = true;

        while (running) {
            System.out.println("Enter your choice (1-5):");
            System.out.println();
            System.out.println(" 1. Create new account without deposit");
            System.out.println(" 2. Create new account with deposit an amount");
            System.out.println(" 3. Deposit an amount to an existing account");
            System.out.println(" 4. Withdraw an amount from an account");
            System.out.println(" 5. Exit");
            System.out.println();
            System.out.print(" Enter your choice: ");
            if (!in.hasNextLine()) break; // input ended
            String choice = in.nextLine().trim();

            switch (choice) {
                case "1":
                    NewAccount.createAccount(in, false);
                    break;
                case "2":
                    NewAccount.createAccount(in, true);
                    break;
                case "3": {
                    Account account = AccessAccount.login(in); // Account reference, AccessAccount object
                    if (account == null) break;
                    double amount = Account.readAmount(in, "Enter amount to be deposited: ");
                    account.deposit(amount); // runs AccessAccount's overriding version
                    break;
                }
                case "4": {
                    Account account = AccessAccount.login(in);
                    if (account == null) break;
                    double amount = Account.readAmount(in, "Enter amount you want to withdraw: ");
                    account.withdraw(amount);
                    break;
                }
                case "5":
                    System.out.println("Goodbye!");
                    running = false;
                    break;
                default:
                    System.out.println("Invalid choice. Please enter a number from 1 to 5.");
            }
        }
        in.close();
    }
}