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    What are different types of design patterns?

    There are three kinds of design patterns:

    Creational patterns:

    They are related with how objects and classes are created. While class-creation patterns use inheritance effectively in the instantiation process,while object-creation patterns use delegation to get the job done.

    * Abstract Factory groups object factories that have a common theme.
    * Builder constructs complex objects by separating construction and representation.
    * Factory Method creates objects without specifying the exact object to create.
    * Prototype creates objects by cloning an existing object.
    * Singleton restricts object creation for a class to only one instance.

    Structural patterns:

    They are related to class and object composition.This pattern uses inheritance to define new interfaces in order to compose new objects and hence new functionalities.

    * Adapter allows classes with incompatible interfaces to work together by wrapping its own interface around that of an already existing class.
    * Bridge decouples an abstraction from its implementation so that the two can vary independently.
    * Composite composes one-or-more similar objects so that they can be manipulated as one object.
    * Decorator dynamically adds/overrides behavior in an existing method of an object.
    * Facade provides a simplified interface to a large body of code.
    * Flyweight reduces the cost of creating and manipulating a large number of similar objects.
    * Proxy provides a placeholder for another object to control access, reduce cost, and reduce complexity.

    Behavioral patterns:

    These design patterns deal with objects communication. They are specifically concerned with communication between objects.

    * Chain of responsibility delegates commands to a chain of processing objects.
    * Command creates objects which encapsulate actions and parameters.
    * Interpreter implements a specialized language.
    * Iterator accesses the elements of an object sequentially without exposing its underlying representation.
    * Mediator allows loose coupling between classes by being the only class that has detailed knowledge of their methods.
    * Memento provides the ability to restore an object to its previous state (undo).
    * Observer is a publish/subscribe pattern which allows a number of observer objects to see an event.
    * State allows an object to alter its behavior when its internal state changes.
    * Strategy allows one of a family of algorithms to be selected on-the-fly at runtime.
    * Template method defines the skeleton of an algorithm as an abstract class, allowing its subclasses to provide concrete behavior.


    1. Very nice.

      Dinesh Lohia

    2. very good site...To prepare for an interview..


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