区分外观模式与服务层模式

// 子系统：库存管理
class InventoryService {
    public boolean checkAvailability(String productId, int quantity) {
        // 检查库存
        return true; // 假设库存充足
    }
}

// 子系统：支付处理
class PaymentService {
    public boolean processPayment(String orderId, double amount) {
        // 处理支付
        return true; // 假设支付成功
    }
}

// 子系统：物流安排
class ShippingService {
    public void arrangeShipping(String orderId, String address) {
        // 安排物流
    }
}

// 外观类
class OrderFacade {
    private InventoryService inventoryService = new InventoryService();
    private PaymentService paymentService = new PaymentService();
    private ShippingService shippingService = new ShippingService();

    public void placeOrder(String productId, int quantity, String address) {
        String orderId = generateOrderId(); // 假设生成订单ID
        double amount = calculateAmount(productId, quantity); // 假设计算订单金额

        if (inventoryService.checkAvailability(productId, quantity)) {
            if (paymentService.processPayment(orderId, amount)) {
                shippingService.arrangeShipping(orderId, address);
                System.out.println("订单已成功下单！");
            } else {
                System.out.println("支付失败！");
            }
        } else {
            System.out.println("库存不足！");
        }
    }

    private String generateOrderId() {
        return "ORDER-" + System.currentTimeMillis();
    }

    private double calculateAmount(String productId, int quantity) {
        return 100.0 * quantity; // 假设单价为100
    }
}

// 客户端代码
public class Client {
    public static void main(String[] args) {
        OrderFacade orderFacade = new OrderFacade();
        orderFacade.placeOrder("PRODUCT-001", 2, "北京市");
    }
}