Lombok’s @Builder annotation is a useful technique to implement the builder pattern that aims to reduce the boilerplate code. In this tutorial, we will learn to apply @Builder to a class and other useful features. Ensure you have included Lombok in the project and installed Lombok support in the IDE. If we want to marshal …
The State pattern lets a delivery respond differently as it moves from packed to shipped to delivered. Follow the Java example, diagrams, and invalid transition.
The Mediator pattern gives interacting objects one place for their coordination rules. Follow a Java chat room that routes messages and rejects an unknown recipient.
The Observer pattern lets a publisher notify registered listeners. Follow a Java example where one listener unsubscribes during a notification and see who receives the next message.
Learn the Memento pattern in Java with an article snapshot example, tested save and restore output, and practical notes on undo history and redo.
Learn the Iterator pattern in Java with a runnable custom Iterable, two traversal orders, exact output, and clear exhaustion and modification behavior.
Learn the Proxy pattern in Java with a runnable lazy report example. See when loading occurs, how repeated reads behave, and the limits of caching and concurrency.
Learn the Flyweight design pattern in Java with a runnable pen factory example. See what state to share, how the cache key works, and when reuse is worthwhile.
Learn the Facade design pattern with a runnable Java report example, clear UML diagrams, and practical guidance on file errors and subsystem access.
The Command pattern turns actions into objects. Build a Java playlist editor with working undo and redo, duplicate-song handling, and clear queueing limits.
Learn the Strategy pattern with UML diagrams and a Java checkout example that applies different discount policies. Includes runnable code and output.
Learn Template Method in Java with shipping quotes, a fixed calculation workflow, required steps, optional hooks, diagrams, and tested failure behavior.
Learn the Composite design pattern with a runnable Java portfolio example. See how leaf and group objects share one operation, and how duplicate membership and overflow affect totals.
Learn the Bridge pattern in Java with a runnable report example. See how report types and output formats vary independently, and when to use Bridge.
Learn the Adapter pattern in Java with a runnable Fahrenheit-to-Celsius example, diagrams, and a failure case that preserves the sensor contract.
Learn the Builder pattern in Java with classic, generic and Lombok implementations. Compare defaults, validation and mutable versus immutable results.
Learn how the Decorator pattern adds optional behavior through Java wrappers. Build a support-report example, trace call order, and run an order-sensitive demo.
Learn Visitor in Java with document export and statistics, complete code, double dispatch, diagrams, and tested visitor reuse and overload behavior.
Learn Chain of Responsibility in Java with ordered discount handlers, working code, diagrams, short-circuit behavior, and explicit no-match handling.
Learn the Prototype pattern in Java with a newsletter campaign example. Compare shallow and deep copies, copy constructors, Cloneable and prototype registries.
Learn Abstract Factory in Java with matching text and GZIP backup readers and writers, working code, diagrams, and incompatible-format handling.
Learn simple factories and Factory Method in Java with working text and HTML preview examples, participant diagrams, output and error handling.
Learn how Java Singleton works with enum and holder implementations, runnable code, thread-safety limits, serialization, and practical alternatives.
HowToDoInJava provides tutorials and how-to guides on Java and related technologies.
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