GoF Design Patterns

Creational Patterns

Name

Description

Factory Patterns

Provide an interface for creating families of related or dependent objects without specifying their concrete classes.

Builder

Separate the construction of a complex object from its representation allowing the same construction process to create various representations.

Factory method

Define an interface for creating an object, but let subclasses decide which class to instantiate. Factory Method lets a class defer instantiation to subclasses (dependency injection^[17]).

Prototype

Specify the kinds of objects to create using a prototypical instance, and create new objects by copying this prototype.

Singleton

Ensure a class has only one instance, and provide a global point of access to it.

Structural Patterns

Adapter

Convert the interface of a class into another interface clients expect. An adapter lets classes work together that could not otherwise because of incompatible interfaces. The enterprise integration pattern equivalent is the Translator.

Bridge

Decouple an abstraction from its implementation allowing the two to vary independently.

Composite

Compose objects into tree structures to represent part-whole hierarchies. Composite lets clients treat individual objects and compositions of objects uniformly.

Decorator

Attach additional responsibilities to an object dynamically keeping the same interface. Decorators provide a flexible alternative to subclassing for extending functionality.

Facade

Provide a unified interface to a set of interfaces in a subsystem. Facade defines a higher-level interface that makes the subsystem easier to use.

Flyweight

Use sharing to support large numbers of similar objects efficiently.

Proxy

Provide a surrogate or placeholder for another object to control access to it.

Behavioural Patterns

Chain of responsibility

Avoid coupling the sender of a request to its receiver by giving more than one object a chance to handle the request. Chain the receiving objects and pass the request along the chain until an object handles it.

Command

Encapsulate a request as an object, thereby letting you parameterize clients with different requests, queue or log requests, and support undoable operations.

Interpreter

Given a language, define a representation for its grammar along with an interpreter that uses the representation to interpret sentences in the language.

Iterator

Provide a way to access the elements of an aggregate object sequentially without exposing its underlying representation.

Mediator

Define an object that encapsulates how a set of objects interact. Mediator promotes loose coupling by keeping objects from referring to each other explicitly, and it lets you vary their interaction independently.

Memento

Without violating encapsulation, capture and externalize an object's internal state allowing the object to be restored to this state later.

Observer or Publish/subscribe

Define a one-to-many dependency between objects where a state change in one object results with all its dependents being notified and updated automatically.

State

Allow an object to alter its behavior when its internal state changes. The object will appear to change its class.

Strategy

Define a family of algorithms, encapsulate each one, and make them interchangeable. Strategy lets the algorithm vary independently from clients that use it.

Template method

Define the skeleton of an algorithm in an operation, deferring some steps to subclasses. Template method lets subclasses redefine certain steps of an algorithm without changing the algorithm's structure.

Visitor

Represent an operation to be performed on the elements of an object structure. Visitor lets you define a new operation without changing the classes of the elements on which it operates.

Name

Description

Active Object

Decouples method execution from method invocation that reside in their own thread of control. The goal is to introduce concurrency, by using asynchronous method invocation and a scheduler for handling requests.

Balking

Only execute an action on an object when the object is in a particular state.

Binding properties

Combining multiple observers to force properties in different objects to be synchronized or coordinated in some way.

Messaging design pattern (MDP)

Allows the interchange of information (i.e. messages) between components and applications.

Double-checked locking

Reduce the overhead of acquiring a lock by first testing the locking criterion (the 'lock hint') in an unsafe manner; only if that succeeds does the actual lock proceed.

Can be unsafe when implemented in some language/hardware combinations. It can therefore sometimes be considered an anti-pattern.

Event-based asynchronous

Addresses problems with the asynchronous pattern that occur in multithreaded programs.

Guarded suspension

Manages operations that require both a lock to be acquired and a precondition to be satisfied before the operation can be executed.

Lock

One thread puts a "lock" on a resource, preventing other threads from accessing or modifying it.

Monitor object

An object whose methods are subject to mutual exclusion, thus preventing multiple objects from erroneously trying to use it at the same time.

Reactor

A reactor object provides an asynchronous interface to resources that must be handled synchronously.

Read-write lock

Allows concurrent read access to an object, but requires exclusive access for write operations.

Scheduler

Explicitly control when threads may execute single-threaded code.

Thread pool

A number of threads are created to perform a number of tasks, which are usually organized in a queue. Typically, there are many more tasks than threads. Can be considered a special case of the object pool pattern.

Thread-specific storage

Static or "global" memory local to a thread.