Java Design Patterns and Constructs

Collection of patterns and other constructs in Java for educational purposes. (See Contributing section if you would like to contribute).

Quickstart

• Install a Java 21 implementation (like openjdk21)
• Clone and run the spring-boot maven goal:

git clone https://github.com/lpenap/java-patterns-and-constructs
cd java-patterns-and-constructs
./mvnw spring-boot:run

Da List

Patterns

• Abstract Factory
• Adapter
• Chain of Responsibility
• Decorator
• Factory
• Factory Method
• Observer
• Singleton
• Strategy
• Template Method

Constructs and Problems

• Producer/Consumer, a multi-process synchronization problem.

Caveats

Change the log level to TRACE in application.properties if you would like to see the output from examples:

logging.level.com.penapereira.example.*=TRACE

Contributing

If you have an interesting idea but don't know how to implement it, feel free to open an issue to request a new feature.

If you would like to contribute additional constructs or patterns follow this steps to add an additional package with the additional example:

1. Create an additional nested package (i.e. newexample) as com.penapereira.example.constructs.newexample
2. Place the interfaces and classes you need there.
3. Implement an example runner by giving it a name ending in ExampleRunner, implementing the ExampleRunnerInterface and adding the @Component annotation:

@Component
public class FooBarExampleRunner implements ExampleRunnerInterface {
	@Override
	public void runExample() {
		// place your code here
	}
}

Additional notes:

• Keep it simple, the idea is to implement the minimum from an educational point of view.
• Try to keep your runtime in less than 1000 milliseconds.
• If you need to output text to the console, try not to print more than 5 lines, you can add a slf4j logger this way and use trace:

@Component
public class FooBarExampleRunner implements ExampleRunnerInterface {
	private static final Logger log = LoggerFactory.getLogger(FooBarExampleRunner.class);
	@Override
	public void runExample() {
		log.trace("Executing FooBar example:");
	}
}