OOP Design Patterns


Object Oriented Programming (OOP) Design Patterns are defined as reusable and tested solution for common object oriented design problems.
They allowed programs to be maintainable, reusable, more flexible and loosely coupled.



Generally these OOP design patterns are divided into 3 categories as Creational, Structural, and Behavioral patterns.
Respective to those 3 categories, there are 23 object oriented design patterns as shown in the given flow diagram.
Out of the above diagram we have pointed out 5 commonly used design patterns.


·       Singleton
This limits creating a class only to one object.
This is achieved through making the constructor as private to that class. 
       This facilitates a global access to an object by ensuring that the object has only one  instance.


·       Factory Method
Normally objects are created without denoting the specific class to which they are created. To overcome this issue, objects are created by calling a factory method without calling to a constructor.
Declare an interface to create an object, but subclasses will choose class to instantiate.

·       Builder
Builder is used to build objects.
Builder separates construction of a complex object and representation
Its object creation is same as abstract factory pattern but in builder pattern creation is done in step by step whereas abstract factory pattern returns the object at once.

·       Adopter
It allows the interface of an existing class to be used as another interface
Adapter acts as a translator which enables communication
Suppose output of one program is in XML format wants to feed to another which requires JSON input, at that point we use an adapter in between in order to coordinate the work.

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