设计模式英文手稿（转）

暑期实习的时候做了一次presentation on design pattern，以下是做的draft(由于公司算半个外企，用的英文;) 

Design patterns are recurring solutions to software design problems you find again and again in real-world application development. 
Patterns are about design and interaction of objects, as well as providing a communication platform concerning elegant, 
reusable solutions to commonly encountered programming challenges. 

They are categorized in three groups: Creational, Structural, and Behavioral. 

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

Factory Method 
definition 
Define an interface for creating an object, but let subclasses decide which class to instantiate. Factory Method lets a class defer instantiation to subclasses. 


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


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


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


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

Bridge 
definition 
Decouple an abstraction from its implementation so that the two can vary independently. 

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

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

Facade 
definition 
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 
definition 
Use sharing to support large numbers of fine-grained objects efficiently. 

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

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

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

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

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

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

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

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

Template 
definition 
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 
definition 
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.