Design Patterns

Design patterns are recurring solutions to software design problems you find again and again in real-world application development. Patterns are about design

and interaction of objects, as well as providing a communication platform.
Design patterns categorized as Creational,Structural,Behavioral.

Creational pattern
Abstract Factory --->Creates an instance of several families of classes
(Provide an interface for creating families of related or dependent objects without specifying their concrete classes.)


Builder --->Separates object construction from its representation
(Separate the construction of a complex object from its representation so that the same construction process can create different representations..)
/>

Factory Method--->Creates an instance of several derived classes
(Define an interface for creating an object, but let subclasses decide which class to instantiate. Factory Method lets a class defer instantiation to subclasses)


Prototype--->A fully initialized instance to be copied or cloned.
(Specify the kind of objects to create using a prototypical instance, and create new objects by copying this prototype.)
/>

Singleton--->A class of which only a single instance can exist.
(Ensure a class has only one instance and provide a global point of access to it.)
/>

Structural pattern
Adapter--->Match interfaces of different classes
(Convert the interface of a class into another interface clients expect. Adapter lets classes work together that couldn't otherwise because of incompatible
interfaces.)


Bridge--->Separates an object’s interface from its implementation
(Decouple an abstraction from its implementation so that the two can vary independently.)


Composite--->A tree structure of simple and composite objects
(Compose objects into tree structures to represent part-whole hierarchies. Composite lets clients treat individual objects and compositions of objects uniformly.

)
/>

Decorator--->Add responsibilities to objects dynamically
(Attach additional responsibilities to an object dynamically. Decorators provide a flexible alternative to subclassing for extending functionality.)
/>

Facade--->A single class that represents an entire subsystem
(Provide a unified interface to a set of interfaces in a subsystem. Façade defines a higher-level interface that makes the subsystem easier to use.)


Flyweight---> A fine-grained instance used for efficient sharing
(Use sharing to support large numbers of fine-grained objects efficiently.)
/>

Proxy--->An object representing another object
(Provide a surrogate or placeholder for another object to control access to it.)
/>


Behavioral pattern
Chain of Resp--->A way of passing a request between a chain of objects
(Avoid coupling the sender of a request to its receiver by giving more than one object a chance to handle the request. Chain the receiving objects and pass the

request along the chain until an object handles it.)
/>

Command--->Encapsulate a command request as an object
(Encapsulate a request as an object, thereby letting you parameterize clients with different requests, queue or log requests, and support undoable operations. )
/>

Interpreter--->A way to include language elements in a program
(Given a language, define a representation for its grammar along with an interpreter that uses the representation to interpret sentences in the language.)
/>

Iterator --->Sequentially access the elements of a collection
(Provide a way to access the elements of an aggregate object sequentially without exposing its underlying representation.)


Mediator--->Defines simplified communication between classes
(Define an object that encapsulates how a set of objects interact. Mediator promotes loose coupling by keeping objects from referring to each other explicitly,

and it lets you vary their interaction independently.)


Memento--->Capture and restore an object's internal state
(Without violating encapsulation, capture and externalize an object's internal state so that the object can be restored to this state later.)


Observer--->A way of notifying change to a number of classes
(Define a one-to-many dependency between objects so that when one object changes state, all its dependents are notified and updated automatically.)


State--->Alter an object's behavior when its state changes
(Define a family of algorithms, encapsulate each one, and make them interchangeable. Strategy lets the algorithm vary independently from clients that use it.)


Strategy---> Encapsulates an algorithm inside a class
(Allow an object to alter its behavior when its internal state changes. The object will appear to change its class.)


Template Method--->Defer the exact steps of an algorithm to a subclasse.
(Define the skeleton of an algorithm in an operation, deferring some steps to subclasses. Template Method lets subclasses redefine certain steps of an

algorithm without changing the algorithm's structure.)


Visitor--->Defines a new operation to a class without change
(Represent an operation to be performed on the elements of an object structure. Visitor lets you define a new operation without changing the classes of the
elements on which it operates.)