Dependency

1// Dependency: PaymentService depends on PaymentGateway
2// but doesn't own it - receives it temporarily
3
4public interface PaymentGateway {
5    boolean processPayment(double amount);
6}
7
8public class StripeGateway implements PaymentGateway {
9    @Override
10    public boolean processPayment(double amount) {
11        System.out.println("Processing $" + amount + " via Stripe");
12        return true;
13    }
14}
15
16public class Order {
17    private String orderId;
18    private double amount;
19    
20    public Order(String orderId, double amount) {
21        this.orderId = orderId;
22        this.amount = amount;
23    }
24    
25    public double getAmount() { return amount; }
26}
27
28public class PaymentService {
29    // No PaymentGateway field - dependency, not association
30    
31    // Depends on Order and PaymentGateway via method parameters
32    public boolean processOrderPayment(Order order, PaymentGateway gateway) {
33        System.out.println("Processing payment for order");
34        return gateway.processPayment(order.getAmount());
35    }
36    
37    // Depends on Order as return type
38    public Order createOrder(String id, double amount) {
39        return new Order(id, amount);
40    }
41}
42
43// Another example with utility dependency
44public class ReportGenerator {
45    // Depends on DateFormatter but doesn't own it
46    public String generateReport(List<Sale> sales, DateFormatter formatter) {
47        StringBuilder report = new StringBuilder();
48        report.append("Sales Report - ").append(formatter.formatDate(new Date()));
49        for (Sale sale : sales) {
50            report.append("
51").append(sale.toString());
52        }
53        return report.toString();
54    }
55}
56
57// Usage
58public class Main {
59    public static void main(String[] args) {
60        PaymentService service = new PaymentService();
61        Order order = service.createOrder("ORD-001", 99.99);
62        PaymentGateway gateway = new StripeGateway();
63        
64        // Gateway is passed in - dependency, not owned
65        service.processOrderPayment(order, gateway);
66    }
67}