BasicATM.java

import java.util.HashMap;
import java.util.Map;

/**
 * BasicATM class - implements ATM interface
 * Demonstrates: interface implementation, singleton pattern.
 */
public class BasicATM implements ATM {
    // Singleton instance
    private static BasicATM instance;

    // Map to track daily withdrawals by account number
    private Map<String, Double> dailyWithdrawals;

    // Private constructor for singleton
    private BasicATM() {
        dailyWithdrawals = new HashMap<>();
    }

    // Singleton access method
    public static synchronized BasicATM getInstance() {
        if (instance == null) {
            instance = new BasicATM();
        }
        return instance;
    }

    @Override
    public boolean validateCard(String cardNumber, String pin) {
        // Basic dummy validation
        return cardNumber.length() == 16 && pin.length() == 4;
    }

    @Override
    public double checkBalance(BankAccount account) {
        return account.getBalance();
    }

    @Override
    public boolean withdrawCash(BankAccount account, double amount) {
        String accountNumber = account.getAccountNumber();

        // Enforce daily limit
        double todayWithdrawal = dailyWithdrawals.getOrDefault(accountNumber, 0.0);
        if (todayWithdrawal + amount > DAILY_WITHDRAWAL_LIMIT) {
            System.out.println("Exceeds daily withdrawal limit.");
            return false;
        }

        boolean success = account.withdraw(amount);

        if (success) {
            dailyWithdrawals.put(accountNumber, todayWithdrawal + amount);
        }

        return success;
    }

    @Override
    public boolean depositFunds(BankAccount account, double amount) {
        return account.deposit(amount);
    }

    // Call this at the end of day to reset limits
    public void resetDailyLimits() {
        dailyWithdrawals.clear();
    }
}