Encapsulation & Access Modifiers

class BankAccount {
    // Private fields — cannot be accessed directly from outside
    private String owner;
    private double balance;
    private String accountNumber;
    
    // Constructor
    public BankAccount(String owner, double initialBalance) {
        this.owner = owner;
        this.balance = initialBalance;
        this.accountNumber = "ACC-" + (int)(Math.random() * 10000);
    }
    
    // Getter methods — read access
    public String getOwner() {
        return owner;
    }
    
    public double getBalance() {
        return balance;
    }
    
    public String getAccountNumber() {
        return accountNumber;
    }
    
    // Controlled methods with validation
    public void deposit(double amount) {
        if (amount > 0) {
            balance += amount;
            System.out.println("Deposited: $" + amount);
        } else {
            System.out.println("Invalid deposit amount!");
        }
    }
    
    public void withdraw(double amount) {
        if (amount > 0 && amount <= balance) {
            balance -= amount;
            System.out.println("Withdrew: $" + amount);
        } else {
            System.out.println("Invalid withdrawal!");
        }
    }
    
    public void printStatement() {
        System.out.println("Account: " + accountNumber);
        System.out.println("Owner: " + owner);
        System.out.println("Balance: $" + balance);
    }
}

public class EncapsulationDemo {
    public static void main(String[] args) {
        BankAccount account = new BankAccount("Alice", 1000);
        
        account.printStatement();
        account.deposit(500);
        account.withdraw(200);
        account.withdraw(5000);  // Will be rejected!
        account.deposit(-100);   // Will be rejected!
        
        System.out.println("\nFinal balance: $" + account.getBalance());
    }
}