BankApp.java

import java.util.*;

public class BankApp {
    private static int nextAccountId = 101;
    private static Scanner scanner = new Scanner(System.in);
    private static Bank activeBank = null;
    private static Map<String, Account> accountRegistry = new HashMap<>();

    public static void main(String[] args) {
        System.out.println("====================================");
        System.out.println("      WELCOME TO BANK MANAGER       ");
        System.out.println("====================================");

        setupBank();
        runBankingSystem();
    }

    private static void setupBank() {
        System.out.println("\nLet's set up your bank!");
        System.out.println("Choose Bank Type:");
        System.out.println("1. Nationalized Bank (Government Owned)");
        System.out.println("2. Cooperative Bank (Community Owned)");
        System.out.print("Enter your choice (1-2): ");

        int choice = readIntegerInput(1, 2);

        System.out.print("\nEnter Bank Name: ");
        String bankName = scanner.nextLine().trim();

        System.out.print("Enter Branch Name: ");
        String branchName = scanner.nextLine().trim();

        if (choice == 1) {
            activeBank = new NationalizedBank(bankName, branchName);
            System.out.println("\nNationalized Bank '" + bankName + "' created successfully!");
        } else {
            activeBank = new CooperativeBank(bankName, branchName);
            System.out.println("\nCooperative Bank '" + bankName + "' created successfully!");
        }
    }

    private static void runBankingSystem() {
        boolean running = true;

        while (running) {
            System.out.println("\n================================");
            System.out.println("         BANKING MENU           ");
            System.out.println("================================");
            System.out.println("1. Open New Account");
            System.out.println("2. Deposit Money");
            System.out.println("3. Withdraw Money");
            System.out.println("4. Display Bank Information");
            System.out.println("5. Exit System");
            System.out.print("\nEnter your choice (1-5): ");

            int choice = readIntegerInput(1, 5);

            switch (choice) {
                case 1:
                    openNewAccount();
                    break;
                case 2:
                    processDeposit();
                    break;
                case 3:
                    processWithdrawal();
                    break;
                case 4:
                    activeBank.displayBankInfo();
                    break;
                case 5:
                    System.out.println("\nThank you for using the Banking System. Goodbye!");
                    running = false;
                    break;
            }

            if (running) {
                System.out.println("\nPress Enter to continue...");
                scanner.nextLine();
            }
        }
    }

    private static void openNewAccount() {
        System.out.println("\n---- OPEN NEW ACCOUNT ----");
        System.out.println("Choose Account Type:");
        System.out.println("1. Savings Account (for personal savings)");
        System.out.println("2. Current Account (for business transactions)");
        System.out.println("3. Loan Account (for borrowing funds)");
        System.out.print("Enter your choice (1-3): ");

        int accountType = readIntegerInput(1, 3);

        System.out.print("\nEnter Account Holder Name: ");
        String holderName = scanner.nextLine().trim();

        String accountNumber = "ACC" + nextAccountId++;

        Account newAccount = null;

        switch (accountType) {
            case 1:
                newAccount = new SavingsAccount(accountNumber, holderName, 0);
                break;
            case 2:
                newAccount = new CurrentAccount(accountNumber, holderName, 0);
                break;
            case 3:
                newAccount = new LoanAccount(accountNumber, holderName, 0);
                break;
        }

        activeBank.openAccount(newAccount);
        accountRegistry.put(accountNumber, newAccount);

        System.out.println("\nAccount created successfully!");
        System.out.println("Your Account Number: " + accountNumber);
        System.out.println("Please make a note of this for future transactions.");
    }

    private static void processDeposit() {
        System.out.println("\n---- DEPOSIT MONEY ----");

        if (accountRegistry.isEmpty()) {
            System.out.println("No accounts have been created yet. Please open an account first.");
            return;
        }

        Account account = findAccount();
        if (account == null) return;

        System.out.print("Enter amount to deposit (₹): ");
        double amount = readPositiveAmount();
        account.deposit(amount);
    }

    private static void processWithdrawal() {
        System.out.println("\n---- WITHDRAW MONEY ----");

        if (accountRegistry.isEmpty()) {
            System.out.println("No accounts have been created yet. Please open an account first.");
            return;
        }

        Account account = findAccount();
        if (account == null) return;

        System.out.print("Enter amount to withdraw (₹): ");
        double amount = readPositiveAmount();
        account.withdraw(amount);
    }

    private static Account findAccount() {
        System.out.print("Enter Account Number: ");
        String accountNumber = scanner.nextLine().trim();
        Account account = accountRegistry.get(accountNumber);

        if (account == null) {
            System.out.println("Account not found. Please check the account number.");
            return null;
        }

        return account;
    }

    private static int readIntegerInput(int min, int max) {
        int value;
        while (true) {
            try {
                String input = scanner.nextLine().trim();
                value = Integer.parseInt(input);
                if (value >= min && value <= max) break;
                else System.out.print("Please enter a number between " + min + " and " + max + ": ");
            } catch (NumberFormatException e) {
                System.out.print("Invalid input. Please enter a number: ");
            }
        }
        return value;
    }

    private static double readPositiveAmount() {
        double amount;
        while (true) {
            try {
                String input = scanner.nextLine().trim();
                amount = Double.parseDouble(input);
                if (amount > 0) break;
                else System.out.print("Please enter a positive amount: ");
            } catch (NumberFormatException e) {
                System.out.print("Invalid input. Please enter a valid amount: ");
            }
        }
        return amount;
    }
}