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Component是基础接口

ConcreteComponent是Component的具体实现类，也就是等等要装饰的类

Decorator是装饰类，它实现Component，并且内部维护一个Component，可以使用构造方法来进行初始化

剩下的就是具体的装饰了

装饰模式，也叫包装模式。说白了，装饰就是用来替代继承的一个方案(比如Java中的BufferedReader就是)，他可以在原来的功能的基础上增加一些功能。

来一个具体的，简单的例子

/*** 基础接口* @author BarryLee* @2018年10月26日@下午8:53:53*/
public interface Car {/*** 最基本的方法--可以跑*/public abstract void run();/*** 展示当前的所有功能*/public abstract void show();
}

/*** 具体实现类，等等要装饰的一个类，实现Car的一个类* @author BarryLee* @2018年10月26日@下午8:54:17*/
public class RunCar implements Car{@Overridepublic void run() {System.out.println("跑");}@Overridepublic void show() {this.run();}}

/*** 装饰类* @author BarryLee* @2018年10月26日@下午9:59:19*/
public class CarDecorator implements Car{private Car car ;public CarDecorator(Car car) {this.car = car;}public Car getCar() {return car;}public void setCar(Car car) {this.car = car;}@Overridepublic void run() {car.run();}@Overridepublic void show() {car.show();}
}	

/*** 具体装饰类1* @author BarryLee* @2018年10月26日@下午9:59:28*/
public class FlyCarDeco extends CarDecorator{public FlyCarDeco(Car car) {super(car);}@Overridepublic void run() {super.getCar().run();}public void fly() {System.out.println("可以飞");}@Overridepublic void show() {super.getCar().show();this.fly();}
}

/*** 具体装饰类2* @author BarryLee* @2018年10月26日@下午9:59:42*/
public class SwimCarDeco extends CarDecorator{public SwimCarDeco(Car car) {super(car);}public void swim() {System.out.println("可以游");}@Overridepublic void show() {super.getCar().show();this.swim();}@Overridepublic void run() {System.out.println("跑");}
}

/*** 测试* @author BarryLee* @2018年10月26日@下午10:00:00*/
public class TestDecorator {@Testpublic void test() {Car car = new RunCar();car.show();//跑}@Testpublic void test1() {Car car = new RunCar();Car flyCar = new FlyCarDeco(car);flyCar.show();/*跑可以飞*/}@Testpublic void test2() {Car car = new RunCar();Car flyCar = new FlyCarDeco(car);flyCar.show();System.out.println("-----");Car swimFlyCar = new SwimCarDeco(flyCar);swimFlyCar.show();/*跑可以飞-----跑可以飞可以游*/}
}

/2019.9.22更新//

下面是Head First 设计模式中的例子

需求是，一个咖啡店，有很多中咖啡，每种咖啡可以搭配不同的调料，要算出价格，同时有一个描述

package cn.bl.decorator.brverage;/*** @Deacription 这是咖啡店，也是测试代码* @Author BarryLee* @Date 2019/9/22 17:05*/
public class Main {public static void main(String[] args) {Beverage b1 = new Espresso();System.out.println(b1.getDescription() + ": " + b1.cost());Beverage b2 = new HouseBlend();b2 = new Mocha(b2);b2 = new Whip(b2);System.out.println(b2.getDescription() + ": " + b2.cost());}
}

package cn.bl.decorator.brverage;/*** @Deacription 饮料抽象类，相当于Conponent* @Author BarryLee* @Date 2019/9/22 17:10*/
public abstract class Beverage {String description = "Unknown description";public String getDescription() {return description;}public abstract double cost();}

package cn.bl.decorator.brverage;/*** @Deacription 浓缩咖啡，饮料的具体实现，相当于ConcreteComponent* @Author BarryLee* @Date 2019/9/22 17:21*/
public class Espresso extends Beverage {/*** 构造器，设置饮料的描述* description来自beverage*/public Espresso() {description = "espresso coffee";}/*** 返回Espresso的价格* @return*/@Overridepublic double cost() {return 1.99;}
}

package cn.bl.decorator.brverage;/*** @Deacription 混合咖啡，相当于ConcreteComponent* @Author BarryLee* @Date 2019/9/22 17:28*/
public class HouseBlend extends Beverage{public HouseBlend() {description = "house blend coffee";}@Overridepublic double cost() {return .89;}
}

package cn.bl.decorator.brverage;/*** @Deacription 调料抽象类，也就是装饰者，相当于类图中的Decorator* 有抽象方法一定就是抽象类** 首先，必须让Condiment Decorator能够取代Beverage* 所以将CondimentDecorator拓展自Beverage** @Author BarryLee* @Date 2019/9/22 17:12*/
public abstract class CondimentDecorator extends Beverage{public abstract String getDescription();}

package cn.bl.decorator.brverage;/*** @Deacription 摩卡调料，是一个具体的装饰者，所以它拓展自CondimentDecorator，相当于ConcreteDecorator* @Author BarryLee* @Date 2019/9/22 22:57*/
public class Mocha extends CondimentDecorator{Beverage beverage;public Mocha(Beverage beverage) {this.beverage = beverage;}@Overridepublic String getDescription() {return beverage.getDescription() + ", mocha";}@Overridepublic double cost() {return beverage.cost() + .20;}
}

package cn.bl.decorator.brverage;/*** @Deacription 泡泡调料，相当于ConcreteDecorator* @Author BarryLee* @Date 2019/9/22 23:12*/
public class Whip extends CondimentDecorator{Beverage beverage;public Whip(Beverage beverage) {this.beverage = beverage;}@Overridepublic String getDescription() {return beverage.getDescription() + ", whip";}@Overridepublic double cost() {return beverage.cost() + .22;}
}

执行结果是

espresso coffee: 1.99
house blend coffee, mocha, whip: 1.31