GoF Design Patterns Masterclass

An interactive guide to the 23 Gang of Four software design patterns with Java & TypeScript implementations, architectural trade-offs, and UML diagrams.

Creational Design Patterns

Mechanisms for creating objects in a manner suitable to the situation:

Factory Method Pattern - Delegate instantiation to subclasses.
Abstract Factory Pattern - Produce families of related objects.
Builder Pattern - Construct complex objects step by step.
Prototype Pattern - Clone existing objects without depending on their concrete classes.
Singleton Pattern - Ensure a class has only one instance with a global access point.

Structural Design Patterns

How classes and objects are composed to form larger structures:

Adapter Pattern - Allow incompatible interfaces to collaborate.
Bridge Pattern - Decouple an abstraction from its implementation.
Composite Pattern - Compose objects into tree structures to represent part-whole hierarchies.
Decorator Pattern - Attach new responsibilities to objects dynamically.
Facade Pattern - Provide a simplified interface to a complex library or subsystem.
Flyweight Pattern - Fit more objects into available RAM by sharing common state.
Proxy Pattern - Provide a placeholder or surrogate to control access to another object.

Behavioral Design Patterns

Algorithms and the assignment of responsibilities between objects:

Chain of Responsibility Pattern - Pass requests along a handler chain.
Command Pattern - Encapsulate requests as stand-alone objects.
Interpreter Pattern - Define a grammar representation and interpreter for a language.
Iterator Pattern - Traverse elements of a collection without exposing underlying representation.
Mediator Pattern - Restrict direct communications between objects and force them to collaborate via a mediator.
Memento Pattern - Save and restore previous states of an object without revealing implementation details.
Observer Pattern - Subscription mechanism to notify multiple observers about state changes.
State Pattern - Alter object behavior when its internal state changes.
Strategy Pattern - Define a family of interchangeable algorithms.
Template Method Pattern - Skeleton of an algorithm in the superclass, letting subclasses override steps.
Visitor Pattern - Separate algorithms from the objects on which they operate.