When to use Strategy pattern in Java?

When to use Strategy pattern in Java?

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The Strategy pattern is a behavioral design pattern that enables an algorithm's variation without changing its code. It allows for implementing different strategies, which encapsulate algorithms and their data, allowing them to be interchanged easily.

In Java, the Strategy pattern can be applied in various scenarios where you need to change the behavior of an object at runtime or make it adaptable to different situations. Here are some common use cases:

When to use the Strategy pattern in Java? You should consider using this pattern when:

By applying the Strategy pattern, you can create a more flexible and extensible design that allows for easy adaptation to different scenarios without modifying the core logic of your application.

Java strategy pattern vs factory example

The age-old debate: Strategy Pattern versus Factory Pattern! Let's dive into the differences and examples to help you decide which one best fits your project needs.

Strategy Pattern

The Strategy Pattern defines a family of algorithms, encapsulates each one as a separate class, and makes them interchangeable at runtime. This allows for algorithm selection based on some external factors or configuration.

In Java, we can illustrate this with an example:

interface PaymentGateway {
void processPayment(Payment payment);
}
class PayPalGateway implements PaymentGateway {
@Override
public void processPayment(Payment payment) {
// process payment via PayPal
}
}
class StripeGateway implements PaymentGateway {
@Override
public void processPayment(Payment payment) {
// process payment via Stripe
}
}
class GatewayFactory {
public static PaymentGateway getGateway(String gatewayType) {
if (gatewayType.equalsIgnoreCase("payPal")) {
return new PayPalGateway();
} else if (gatewayType.equalsIgnoreCase("stripe")) {
return new StripeGateway();
} else {
throw new RuntimeException("Unsupported gateway type");
}
}
}
public class PaymentProcessor {
private PaymentGateway paymentGateway;
public PaymentProcessor(String gatewayType) {
paymentGateway = GatewayFactory.getGateway(gatewayType);
}
public void processPayment(Payment payment) {
paymentGateway.processPayment(payment);
}
}

In this example, we have a PaymentGateway interface that defines the algorithm for processing payments. We then create concrete implementations (PayPalGateway and StripeGateway) that encapsulate these algorithms. The GatewayFactory class helps us select the correct implementation based on the provided gateway type.

Factory Pattern

The Factory Pattern provides an interface for creating objects, but allows subclasses to decide which classes to instantiate. This approach promotes abstraction and decouples object creation from client code.

Let's explore this in Java:

interface PaymentGateway {
void processPayment(Payment payment);
}
class PayPalGateway implements PaymentGateway {
@Override
public void processPayment(Payment payment) {
// process payment via PayPal
}
}
class StripeGateway implements PaymentGateway {
@Override
public void processPayment(Payment payment) {
// process payment via Stripe
}
}
abstract class GatewayFactory {
abstract PaymentGateway createGateway();
}
class PayPalGatewayFactory extends GatewayFactory {
@Override
public PaymentGateway createGateway() {
return new PayPalGateway();
}
}
class StripeGatewayFactory extends GatewayFactory {
@Override
public PaymentGateway createGateway() {
return new StripeGateway();
}
}
public class PaymentProcessor {
private PaymentGateway paymentGateway;
public PaymentProcessor(GatewayFactory factory) {
paymentGateway = factory.createGateway();
}
public void processPayment(Payment payment) {
paymentGateway.processPayment(payment);
}
}

In this example, we have an abstract GatewayFactory class that defines the interface for creating gateways. We then create concrete subclasses (PayPalGatewayFactory and StripeGatewayFactory) that implement this interface by returning the correct gateway instances.

Key Differences

When to use each:

In conclusion, while both patterns share similarities in promoting abstraction and decoupling, the Strategy Pattern is more focused on algorithm selection, whereas the Factory Pattern emphasizes object creation. Choose wisely, depending on your project needs!