How many design patterns are there and what are they?

 Posted by Raja on 5/14/2010 | Category: Design Pattern & Practices Interview questions | Views: 21590

According to Gang Of Four, there are three types of Design Pattern (Visit for more details)

1. Creational
2. Structural
3. Behavioral

Creational Design Pattern

Abstract Factory - Creates an instance of several families of classes
Builder - Separates object construction from its representation
Factory Method - Creates an instance of several derived classes
Prototype - A fully initialized instance to be copied or cloned
Singleton - A class of which only a single instance can exist

Structural Design Pattern

Adapter - Match interfaces of different classes
Bridge - Separates an object’s interface from its implementation
Composite - A tree structure of simple and composite objects
Decorator - Add responsibilities to objects dynamically
Facade - A single class that represents an entire subsystem
Flyweight - A fine-grained instance used for efficient sharing
Proxy - An object representing another object

Behavioral Design Pattern

Chain of Resp. - A way of passing a request between a chain of objects
Command - Encapsulate a command request as an object
Interpreter - A way to include language elements in a program
Iterator - Sequentially access the elements of a collection
Mediator - Defines simplified communication between classes
Memento - Capture and restore an object's internal state
Observer - A way of notifying change to a number of classes
State - Alter an object's behavior when its state changes
Strategy - Encapsulates an algorithm inside a class
Template Method - Defer the exact steps of an algorithm to a subclass
Visitor - Defines a new operation to a class without change

Above pattern and description has been copied from for information and knowledge purpose.

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