Facade

1// Complex subsystem classes
2class Inventory {
3    public boolean checkStock(String productId) {
4        System.out.println("Checking inventory for: " + productId);
5        return true;
6    }
7    
8    public void reserveItem(String productId) {
9        System.out.println("Reserving item: " + productId);
10    }
11}
12
13class PaymentProcessor {
14    public boolean validateCard(String cardNumber) {
15        System.out.println("Validating card: " + cardNumber);
16        return true;
17    }
18    
19    public boolean chargeCard(String cardNumber, double amount) {
20        System.out.println("Charging $" + amount + " to card");
21        return true;
22    }
23}
24
25class ShippingService {
26    public String calculateShipping(String address) {
27        System.out.println("Calculating shipping to: " + address);
28        return "3-5 business days";
29    }
30    
31    public void scheduleDelivery(String orderId, String address) {
32        System.out.println("Scheduling delivery for order: " + orderId);
33    }
34}
35
36class NotificationService {
37    public void sendEmail(String email, String message) {
38        System.out.println("Sending email to: " + email);
39    }
40    
41    public void sendSMS(String phone, String message) {
42        System.out.println("Sending SMS to: " + phone);
43    }
44}
45
46// Facade - simplified interface
47class OrderFacade {
48    private Inventory inventory;
49    private PaymentProcessor payment;
50    private ShippingService shipping;
51    private NotificationService notification;
52    
53    public OrderFacade() {
54        this.inventory = new Inventory();
55        this.payment = new PaymentProcessor();
56        this.shipping = new ShippingService();
57        this.notification = new NotificationService();
58    }
59    
60    // Simple method that orchestrates complex operations
61    public boolean placeOrder(String productId, String cardNumber, 
62                              double amount, String address, String email) {
63        System.out.println("\n=== Processing Order ===");
64        
65        // Step 1: Check inventory
66        if (!inventory.checkStock(productId)) {
67            notification.sendEmail(email, "Product out of stock");
68            return false;
69        }
70        
71        // Step 2: Process payment
72        if (!payment.validateCard(cardNumber)) {
73            notification.sendEmail(email, "Invalid card");
74            return false;
75        }
76        
77        if (!payment.chargeCard(cardNumber, amount)) {
78            notification.sendEmail(email, "Payment failed");
79            return false;
80        }
81        
82        // Step 3: Reserve item
83        inventory.reserveItem(productId);
84        
85        // Step 4: Schedule shipping
86        String orderId = "ORD-" + System.currentTimeMillis();
87        shipping.scheduleDelivery(orderId, address);
88        
89        // Step 5: Notify customer
90        notification.sendEmail(email, "Order " + orderId + " confirmed!");
91        
92        System.out.println("=== Order Complete ===\n");
93        return true;
94    }
95}
96
97// Usage - client only needs to know about Facade
98public class Main {
99    public static void main(String[] args) {
100        OrderFacade orderFacade = new OrderFacade();
101        
102        // One simple call instead of managing 5 subsystems
103        orderFacade.placeOrder(
104            "PROD-123",
105            "1234-5678-9012-3456",
106            99.99,
107            "123 Main St",
108            "customer@email.com"
109        );
110    }
111}