Decorator design pattern

DecoratorDemo

package com.company;

interface Shape{

    void draw();

}

class Circle implements Shape{

     public void draw()
     {

         System.out.println("Draw a Circle");

     }

}

abstract class ShapeDecorator implements Shape{

    Shape decoratedShape;

    ShapeDecorator(Shape s){

        this.decoratedShape = s;

    }

    public void draw(){

        decoratedShape.draw();

    };

}

 class RedCircle extends ShapeDecorator{

    RedCircle(Shape s)
    {
        super(s);
    }


    @Override
    public void draw(){

        decoratedShape.draw();
        drawRedBorder();

    }

    public void drawRedBorder(){

        System.out.println("Draw a Red Border for the circle");

    }

}

public class DecoratorDemo {

    public static void main(String[] args){

        Shape circle = new Circle();
        circle.draw();

        Shape redcircle = new RedCircle(circle);
        redcircle.draw();

    }
}

/*
* 1. ShapeDecorator class should be an abstract class, which implements shape interface;
* 2. ShapeDecorator should accept a shape instance as input for constructor.
* 3. concrete decorator class should extends the ShapeDecorator and override the decorated method.
* By doing so, we can add more functionalities to Circle() object, without changing its original class definition.
*
*
* */