Design patterns are not mandatory templates.
They are names for recurring design problems and proven ways of solving them. Knowing them helps you understand frameworks, review code and communicate architectural decisions. 🚀
🇫🇷 France may have lost the World Cup… but here is a small consolation prize for Java developers. 😅☕
Turn the disappointment into learning with my course on Java Design Patterns and strengthen your software design skills.
🏆 We may not have won the cup, but you can still master Strategy, Factory, Builder, Adapter and many more!
IT IS FREE 🆓
#Java #DesignPatterns #JavaDeveloper #SoftwareEngineering #Learning #WorldCup
🔸 TL;DR
▪️ Learn the problem behind each pattern, not only its class diagram.
▪️ Use patterns to simplify change, not to make code look “architectural.”
▪️ Start with Strategy, Builder, Factory, Adapter and Decorator.
🔸 1. STRATEGY
interface Discount { double apply(double price); } var finalPrice = discount.apply(100);
var finalPrice = discount.apply(100);
Strategy moves interchangeable behavior behind an interface.
Use it when an algorithm, validation rule or business policy may change independently.
🔸 2. FACTORY METHOD
Notification create(String type) { return switch (type) { case "EMAIL" -> new EmailNotification(); default -> new SmsNotification(); }; }
A factory centralizes object creation.
Callers request an abstraction without knowing the concrete implementation.
🔸 3. BUILDER
var user = User.builder()
.name("Duke")
.email("duke@java.dev")
.active(true)
.build();Builder makes complex object construction readable.
It is especially useful for immutable objects with several optional fields.
🔸 4. ADAPTER
class PaymentAdapter implements PaymentService { public void pay(BigDecimal amount) { legacyGateway.execute(amount.doubleValue()); } }
Adapter converts one API into another expected interface.
It is common when integrating legacy code, SDKs and external services.
🔸 5. DECORATOR
Service service =
new LoggingService(
new RetryService(
new RemoteService()));Decorator adds behavior around an existing object without changing its implementation.
Logging, retries, caching and metrics are common examples.
🔸 6. OBSERVER
orderEvents.subscribe(emailListener);
orderEvents.publish(new OrderCreated(orderId));Observer lets multiple listeners react to an event.
It enables loose coupling, but uncontrolled event chains can make execution difficult to trace.
🔸 7. TEMPLATE METHOD
abstract class Importer { final void run() { read(); validate(); save(); } abstract void read(); }
Template Method defines the workflow while subclasses customize selected steps.
Framework lifecycle hooks frequently use this idea.
🔸 8. COMMAND
interface Command { void execute(); } queue.add(() -> invoiceService.generate(id));
Command represents an operation as an object.
This makes actions easier to queue, retry, log, schedule or undo.
🔸 9. FACADE
checkoutFacade.checkout(cart, customer);
Facade exposes one simple entry point over several services or subsystems.
The caller does not need to coordinate inventory, payment and delivery itself.
🔸 10. PROXY
class SecuredService implements Service { public void execute() { security.checkAccess(); target.execute(); } }
Proxy controls access to another object.
It can introduce security, lazy loading, transactions, caching or remote communication.
Spring AOP and Hibernate proxies rely heavily on this principle.
🔸 TAKEAWAYS
▪️ Strategy isolates changing business behavior.
▪️ Factory and Builder simplify object creation.
▪️ Adapter and Facade simplify integration.
▪️ Decorator and Proxy wrap existing behavior for different purposes.
▪️ Observer and Command decouple producers from execution.
▪️ Template Method standardizes workflows.
▪️ A pattern is useful only when it makes the design easier to understand and change.
The best developers do not use the most patterns.
They recognize when a pattern solves a real problem—and when a simple method is enough. ☕🧠
#Java #DesignPatterns #SoftwareEngineering #SoftwareArchitecture #CleanCode #ObjectOrientedProgramming #SpringBoot #JavaDeveloper #Programming #Developer
Go further with Java certification:
Java👇
Spring👇
SpringBook👇
JavaBook👇