Software Design Patterns

Creational Patterns

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

Separate the construction of a complex object from its representation so that 
the same construction process can create different representations.

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

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

Structural Patterns

Convert the interface of a class into another interface clients expect. Adapter 
lets classes work together that couldn't otherwise because of incompatible 

Decouple an abstraction from its implementation so that the two can vary 

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

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

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.

Use sharing to support large numbers of fine=grained objects efficiently.

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

Behavioral 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.

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

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

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

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.

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

Define a one-to-many dependency between objects so that when one object changes 
state, all its dependents are notified and updated automatically.

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

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.

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.
" Design Patterns: Elements of Reusable Object-Oriented Software Erich 
Gamma,Richard Helm,Ralph Johnson, John Vlissides