Decorator pattern - Structural

• Add additional responsibilities dynamically to an object. 
• Add new functionality to an existing object without altering its structure
• creates a decorator class which wraps the original class and provides additional functionality
• Also known as Wrapper

Where to use ?

• To add new function to an object without affecting other objects
• To make a responsibility easily added and removed dynamically.

Implementation example

• Interface Shape implemented by multiple concrete classes : Circle, Rectangle, Square
• Client uses concrete classes.

      After introducing decorator :

• Create another interface ShapeDecorator extending Shape interface
• Create concrete class RedShapeDecorator implementing ShapeDecorator
• Client can use decorator class to get additional behavior