Design Patterns Tutorial
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- Transfer Object Pattern
- Service Locator Pattern
- Intercepting Filter Pattern
- Front Controller Pattern
- Data Access Object Pattern
- Composite Entity Pattern
- Business Delegate Pattern
- Design Patterns - MVC Pattern
- Design Patterns - Visitor Pattern
- Design Patterns - Template Pattern
- Design Patterns - Strategy Pattern
- Design Patterns - Null Object Pattern
- Design Patterns - State Pattern
- Design Patterns - Observer Pattern
- Design Patterns - Memento Pattern
- Design Patterns - Mediator Pattern
- Design Patterns - Iterator Pattern
- Design Patterns - Interpreter Pattern
- Design Patterns - Command Pattern
- Chain of Responsibility Pattern
- Design Patterns - Proxy Pattern
- Design Patterns - Flyweight Pattern
- Design Patterns - Facade Pattern
- Design Patterns - Decorator Pattern
- Design Patterns - Composite Pattern
- Design Patterns - Filter Pattern
- Design Patterns - Bridge Pattern
- Design Patterns - Adapter Pattern
- Design Patterns - Prototype Pattern
- Design Patterns - Builder Pattern
- Design Patterns - Singleton Pattern
- Abstract Factory Pattern
- Design Patterns - Factory Pattern
- Design Patterns - Overview
- Design Patterns - Home
Design Patterns Resources
- Design Patterns - Discussion
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- Design Patterns - Quick Guide
- Design Patterns - Questions/Answers
Selected Reading
- Who is Who
- Computer Glossary
- HR Interview Questions
- Effective Resume Writing
- Questions and Answers
- UPSC IAS Exams Notes
Design Patterns - Overview
Design Pattern - Overview
Design patterns represent the best practices used by experienced object-oriented software developers. Design patterns are solutions to general problems that software developers faced during software development. These solutions were obtained by trial and error by numerous software developers over quite a substantial period of time.
What is Gang of Four (GOF)?
In 1994, four authors Erich Gamma, Richard Helm, Ralph Johnson and John Vpssides pubpshed a book titled Design Patterns - Elements of Reusable Object-Oriented Software which initiated the concept of Design Pattern in Software development.
These authors are collectively known as Gang of Four (GOF). According to these authors design patterns are primarily based on the following principles of object orientated design.
Program to an interface not an implementation
Favor object composition over inheritance
Usage of Design Pattern
Design Patterns have two main usages in software development.
Common platform for developers
Design patterns provide a standard terminology and are specific to particular scenario. For example, a singleton design pattern signifies use of single object so all developers famipar with single design pattern will make use of single object and they can tell each other that program is following a singleton pattern.
Best Practices
Design patterns have been evolved over a long period of time and they provide best solutions to certain problems faced during software development. Learning these patterns helps unexperienced developers to learn software design in an easy and faster way.
Types of Design Patterns
As per the design pattern reference book Design Patterns - Elements of Reusable Object-Oriented Software , there are 23 design patterns which can be classified in three categories: Creational, Structural and Behavioral patterns. We ll also discuss another category of design pattern: J2EE design patterns.
| S.N. | Pattern & Description |
|---|---|
| 1 | Creational Patterns These design patterns provide a way to create objects while hiding the creation logic, rather than instantiating objects directly using new operator. This gives program more flexibipty in deciding which objects need to be created for a given use case. |
| 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 functionapties. |
| 3 | Behavioral Patterns These design patterns are specifically concerned with communication between objects. |
| 4 | J2EE Patterns These design patterns are specifically concerned with the presentation tier. These patterns are identified by Sun Java Center. |