Single Responsibility Principle with Example
Understand the single responsibility principle with a Java example. Separate employee storage from email delivery and see where workflow coordination belongs.
Design patterns represent the best practices used by experienced object-oriented software developers. Design patterns are solutions to general problems that software developers faced during software development. These solutions were obtained by trial and error by numerous software developers over quite a substantial period of time.
Uses of Design Patterns
Design patterns can speed up the development process by providing tested, proven development paradigms. Effective software design requires considering issues that may not become visible until later in the implementation. Reusing design patterns helps to prevent subtle issues that can cause major problems and improves code readability for coders and architects familiar with the patterns.
Often, people only understand how to apply certain software design techniques to certain problems. These techniques are difficult to apply to a broader range of problems. Design patterns provide general solutions, documented in a format that doesn’t require specifics tied to a particular problem.
In addition, patterns allow developers to communicate using well-known, well understood names for software interactions. Common design patterns can be improved over time, making them more robust than ad-hoc designs.
The 23 Gang of Four (GoF) patterns are generally considered the foundation for all other patterns. Let us learn with examples.
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Tutorials
State Design Pattern in Java
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.
Mediator Design Pattern in Java
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.
Observer Design Pattern in Java
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.
Memento Design Pattern in Java
Learn the Memento pattern in Java with an article snapshot example, tested save and restore output, and practical notes on undo history and redo.
Iterator Design Pattern in Java with a Custom Iterable
Learn the Iterator pattern in Java with a runnable custom Iterable, two traversal orders, exact output, and clear exhaustion and modification behavior.
Proxy Design Pattern in Java
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.
Flyweight Design Pattern in Java
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.
Facade Design Pattern in Java
Learn the Facade design pattern with a runnable Java report example, clear UML diagrams, and practical guidance on file errors and subsystem access.
Command Design Pattern in Java: Undo, Redo and Queues
The Command pattern turns actions into objects. Build a Java playlist editor with working undo and redo, duplicate-song handling, and clear queueing limits.
Strategy Design Pattern in Java
Learn the Strategy pattern with UML diagrams and a Java checkout example that applies different discount policies. Includes runnable code and output.
Template Method Design Pattern in Java
Learn Template Method in Java with shipping quotes, a fixed calculation workflow, required steps, optional hooks, diagrams, and tested failure behavior.
Composite Design Pattern in Java
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.
Bridge Design Pattern in Java
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.
Adapter Design Pattern in Java
Learn the Adapter pattern in Java with a runnable Fahrenheit-to-Celsius example, diagrams, and a failure case that preserves the sensor contract.
Builder Design Pattern in Java
Learn the Builder pattern in Java with classic, generic and Lombok implementations. Compare defaults, validation and mutable versus immutable results.
Decorator Design Pattern in Java
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.
Visitor Design Pattern in Java
Learn Visitor in Java with document export and statistics, complete code, double dispatch, diagrams, and tested visitor reuse and overload behavior.
Chain of Responsibility Design Pattern in Java
Learn Chain of Responsibility in Java with ordered discount handlers, working code, diagrams, short-circuit behavior, and explicit no-match handling.
Prototype Design Pattern in Java
Learn the Prototype pattern in Java with a newsletter campaign example. Compare shallow and deep copies, copy constructors, Cloneable and prototype registries.
Abstract Factory Design Pattern in Java
Learn Abstract Factory in Java with matching text and GZIP backup readers and writers, working code, diagrams, and incompatible-format handling.
Factory Design Pattern in Java
Learn simple factories and Factory Method in Java with working text and HTML preview examples, participant diagrams, output and error handling.
Singleton Design Pattern in Java
Learn how Java Singleton works with enum and holder implementations, runnable code, thread-safety limits, serialization, and practical alternatives.