ATMSimulation.java

import java.util.*;

// Base class representing a Bank Account
class Account {
 protected double balance;
 protected int pin;

 public Account(double initialBalance, int pin) {
 this.balance = initialBalance;
 this.pin = pin;
 }

 public boolean verifyPIN(int enteredPIN) {
 return this.pin == enteredPIN;
 }

 public double getBalance() {
 return balance;
 }

 public void deposit(double amount) {
 if (amount <= 0) {
 throw new IllegalArgumentException("Deposit amount must be positive.");
 }
 balance += amount;
 }

 public void withdraw(double amount) {
 if (amount <= 0) {
 throw new IllegalArgumentException("Withdrawal amount must be positive.");
 }
 if (amount > balance) {
 throw new IllegalArgumentException("Insufficient funds.");
 }
 balance -= amount;
 }
}

// Derived class representing a specific type of Account (Savings)
class SavingsAccount extends Account {
 public SavingsAccount(double initialBalance, int pin) {
 super(initialBalance, pin);
 }

 // Example of inheritance: adding specific behavior
 public void addInterest(double rate) {
 if (rate < 0) throw new IllegalArgumentException("Interest rate cannot be negative.");
 balance += balance * rate / 100;
 }
}

// ATM class handles multiple accounts using a Collection
class ATMSimulation {
 private static final Scanner scanner = new Scanner(System.in);
 private static final Map<Integer, SavingsAccount> accounts = new HashMap<>(); // Stores accounts by account number
 private static SavingsAccount currentAccount;

 public static void main(String[] args) {
 // Sample accounts
 accounts.put(1001, new SavingsAccount(1000.00, 1234));
 accounts.put(1002, new SavingsAccount(500.00, 5678));
 accounts.put(1003, new SavingsAccount(1500.00, 4321));

 System.out.println("=== Welcome to the ATM Simulation ===");

 try {
 login();
 showMenu();
 } catch (Exception e) {
 System.out.println("Error: " + e.getMessage());
 } finally {
 System.out.println("Thank you for using the ATM!");
 }
 }

 private static void login() {
 int attempts = 0;
 while (attempts < 3) {
 System.out.print("\nEnter Account Number: ");
 int accNum = scanner.nextInt();
 System.out.print("Enter PIN: ");
 int enteredPIN = scanner.nextInt();

 SavingsAccount account = accounts.get(accNum);
 if (account != null && account.verifyPIN(enteredPIN)) {
 currentAccount = account;
 System.out.println("Login successful!\n");
 return;
 } else {
 attempts++;
 System.out.println("Invalid account number or PIN. Attempts left: " + (3 - attempts));
 }
 }
 throw new SecurityException("Too many failed attempts. Access denied.");
 }

 private static void showMenu() {
 while (true) {
 System.out.println("\n--- ATM Menu ---");
 System.out.println("1. Check Balance");
 System.out.println("2. Deposit");
 System.out.println("3. Withdraw");
 System.out.println("4. Add Interest");
 System.out.println("5. Exit");
 System.out.print("Choose an option: ");

 try {
 int choice = scanner.nextInt();
 switch (choice) {
 case 1 -> checkBalance();
 case 2 -> deposit();
 case 3 -> withdraw();
 case 4 -> addInterest();
 case 5 -> {
 System.out.println("Session ended. Goodbye!");
 return;
 }
 default -> System.out.println("Invalid choice. Please try again.");
 }
 } catch (InputMismatchException e) {
 System.out.println("Invalid input. Please enter a number.");
 scanner.nextLine(); // clear input buffer
 } catch (IllegalArgumentException e) {
 System.out.println("Error: " + e.getMessage());
 }
 }
 }

 private static void checkBalance() {
 System.out.printf("Your current balance is: Rs.%.2f%n", currentAccount.getBalance());
 }

 private static void deposit() {
 System.out.print("Enter deposit amount: ");
 double amount = scanner.nextDouble();
 currentAccount.deposit(amount);
 System.out.printf("Rs.%.2f deposited successfully.%n", amount);
 }

 private static void withdraw() {
 System.out.print("Enter withdrawal amount: ");
 double amount = scanner.nextDouble();
 
 currentAccount.withdraw(amount);
 System.out.printf("Rs.%.2f withdrawn successfully.%n", amount);
 }

 private static void addInterest() {
 System.out.print("Enter interest rate (%): ");
 double rate = scanner.nextDouble();
 currentAccount.addInterest(rate);
 System.out.println("Interest added successfully!");
 }
}