Design Pattern - Introduction

Design Pattern - Introduction

Design Patterns are best practices how to solve common know problems , in another words well-proved solution for solving the specific problem.

These best practices used by experienced object-oriented software developers and these are programming language independent.

By using design patterns make the code:

    * flexible

    * reusable

    * maintainable

Every design pattern has some specification or set of rules for solving the problems.

Advantages of Design Patterns :

    * reusable in multiple projects

    * provide solutions that helps to design software architecture

    * follow software engineering experiences

    * provide transparency of the design of an application

    * well-proved and testified solutions

When we use the Design patterns

We must use the design patterns during the analysis and requirement phase of SDLC ( Software Development Life Cycle ).

Design Patterns can be divided into:

 

1. Creational Patterns

These design patterns provides way to create objects while hiding the creation logic, rather than instantiating objects directly using new operator.

This gives program more flexibility in deciding which objects need to be created for a given use case.

Example:

    Factory Pattern

    Abstract Factory Pattern

    Singleton Pattern

    Prototype Pattern

    Builder Pattern

2. Structural Patterns

These design patterns concern class and object composition.

Concept of inheritance is used to compose interfaces and define ways to compose objects to obtain new functionalities.

Example:

    Adapter Pattern

    Bridge Pattern

    Composite Pattern

    Decorator Pattern

    Facade Pattern

    Flyweight Pattern

    Proxy Pattern

3. Behavioral Patterns

These design patterns are specifically concerned with communication between objects.

Example:

    Chain of Responsibility Pattern

    Command Pattern

    Interpreter Pattern

    Iterator Pattern

    Mediator Pattern

    Memento Pattern

    Observer Pattern

    State Pattern

    Strategy Pattern

    Template Pattern

    Visitor Pattern

4. JavaEE Design Patterns

* Presentation Layer Design Pattern

* Business Layer Design Pattern

* Data Layer Design Pattern