A Humorous Introduction to 23 Classic Design Patterns

01 Factory Method

The Factory Method pattern separates the client from the concrete product creation; the client simply asks the factory for a product, allowing new products to be added without changing client code, though the factory itself must be updated when products change.

02 Builder Pattern

The Builder pattern decouples a product’s internal representation from its construction process, enabling the same construction steps to create different representations and allowing the product’s internal structure to vary independently of the client.

03 Abstract Factory

The Abstract Factory pattern delegates the creation of families of related objects to concrete factories, letting the client specify what it needs while the specific factory determines the exact product, thus avoiding direct coupling to concrete classes.

04 Prototype Pattern

The Prototype pattern creates new objects by cloning an existing prototype instance, allowing dynamic addition or removal of product types without a predefined class hierarchy, but each class must implement a cloning method.

05 Singleton Pattern

The Singleton pattern ensures that a class has only one instance and provides a global point of access to it, suitable only when a true single instance is required.

06 Adapter Pattern

The Adapter pattern converts one interface into another expected by the client, enabling incompatible classes to work together by returning an appropriate instance based on parameters.

07 Bridge Pattern

The Bridge pattern decouples abstraction from implementation, allowing both to vary independently by using composition/aggregation instead of inheritance.

08 Composite Pattern

The Composite pattern organizes objects into tree structures to represent whole-part hierarchies, allowing clients to treat individual objects and compositions uniformly.

09 Decorator Pattern

The Decorator pattern adds responsibilities to objects dynamically and transparently, offering a flexible alternative to subclassing by stacking basic functionalities.

10 Facade Pattern

The Facade pattern provides a high‑level interface that makes a subsystem easier to use, often implemented as a single instance (sometimes a Singleton) that simplifies complex interactions.

11 Flyweight Pattern

The Flyweight pattern shares fine‑grained objects to reduce memory usage by separating intrinsic (shared) state from extrinsic (context‑dependent) state.

12 Proxy Pattern

The Proxy pattern supplies a surrogate object that controls access to the real subject, allowing additional behavior such as request filtering or lazy initialization.

13 Chain of Responsibility Pattern

The Chain of Responsibility pattern links handlers in a chain so that a request traverses the chain until a handler processes it, enabling dynamic reconfiguration without client awareness.

14 Command Pattern

The Command pattern encapsulates a request as an object, separating the invoker from the executor, supporting undoable operations and flexible command management.

15 Interpreter Pattern

The Interpreter pattern defines a representation for a language’s grammar and provides an interpreter to evaluate sentences, allowing the definition of a class hierarchy for expressions.

16 Iterator Pattern

The Iterator pattern provides a way to sequentially access elements of a collection without exposing its internal structure, encapsulating traversal logic in a separate iterator object.

17 Mediator Pattern

The Mediator pattern encapsulates how a set of objects interact, promoting loose coupling by centralizing communication through a mediator rather than direct references.

18 Memento Pattern

The Memento pattern captures an object’s internal state in a snapshot object so that it can be restored later without violating encapsulation.

19 Observer Pattern

The Observer pattern defines a one‑to‑many dependency so that when the subject changes state, all its observers are automatically notified and updated.

20 State Pattern

The State pattern allows an object to alter its behavior when its internal state changes, appearing as if the object has changed its class.

21 Strategy Pattern

The Strategy pattern defines a family of algorithms, encapsulates each one, and makes them interchangeable, letting the algorithm vary independently from clients.

22 Template Method Pattern

The Template Method pattern defines the skeleton of an algorithm in a base class, deferring some steps to subclasses to provide specific implementations.

23 Visitor Pattern

The Visitor pattern separates an algorithm from the object structure it operates on, allowing new operations to be added without modifying the existing object classes.