装饰器模式 -- 设计模式

装饰器模式（Decorator Pattern）允许向一个现有的对象添加新的功能，同时又不改变其结构。

思考: 装饰器和原型实现了同一个接口, 然后装饰器包装了原型

package day0319.DecoratorPattern;


public class Demo{

    public static void main(String[] args){

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

        System.out.println("with out Decorator");
        new Circle().draw();
    }
}

interface Shape {
    void draw();
}

abstract class ShapeDecorator implements Shape {
    Shape shape;

    public ShapeDecorator(Shape shape){
        this.shape = shape;
    }

    public abstract void draw();
}

class RedShapeDecorator extends ShapeDecorator{


    public RedShapeDecorator(Shape shape){
        super(shape);
    }

    @Override
    public void draw(){
        System.out.println("我先是拿起了一支红色的彩色铅笔");
        System.out.println("然后我把画纸铺平");
        System.out.println("我小心的将身子趴在桌子上");
        super.shape.draw();
        System.out.println("最后我小心的把我的作品卷了起来, 放好");
    }
}


/************************** 构造两个shape的实现类 *************************/
class Circle implements Shape {

    @Override
    public void draw(){
        System.out.println("画了一个圆");
    }
}
class Rectangle implements Shape {

    @Override
    public void draw(){
        System.out.println("画了一个四边形");
    }
}