What are design patterns?

The Design patterns are recurring solution to the recurring problems in the software architecture. There are 3 basic classification of patterns Behavioral patterns,Creational, and Structural   patterns.

Creational Patterns:

• Abstract Factory:- This Creates an instance of the several families of classes.
• Builder :- It Separates object construction from its representation.
• Factory Method:- It Creates an instance of the several derived classes.
• Prototype:- The fully initialized instance to be cloned or copied.
• Singleton:- The class in which only a single instance can be exist.

Structural Patterns:

• Adapter:-In this interfaces of different classes are matched.
• Bridge:-It Separates an object's interface from its implementation.
• Composite:-A tree structure of the simple and composite objects.
• Decorator :-It Add authorities to the objects dynamically.
• Façade:-The single class which represents the whole subsystem.
• Flyweight:-It is a fine-grained instance used for effective sharing.
• Proxy:- The object representing the other object.

Behavioral Patterns:

• Mediator:-It Defines the simplified communication between classes.
• Memento:-It Captures & restore an object's internal state.
• Interpreter:-A way to include the language elements in the program.
• Strategy:-It Encapsulates the algorithm inside a class.
• Observer:-A way of notifying change to a no. of classes.
• Template Method:-Defer the exact points of an algorithm to a subclass.
• Visitor:-It Defines a new operation to a class without change.
• Iterator:-It Sequentially access the elements of a collection.
• Chain of Resp:-A way of passing a request b/w a chain of objects.
• Command:-It Encapsulate a command request as an object.
• State:-whenever its state changes alter an object's behavior.