学习笔记之装饰者模式

装饰者（Decorator）模式又名包装（Wrapper）模式，它动态地将责任附加到对象上。若要扩展功能，装饰者提供了比继承更有弹性的替代方案。

[code]

package org.kangsg219.abst;

//星巴兹咖啡抽象类

public abstract class Beverage {

public String description="Unknown Beverage!";

public String getDescription(){

return description;

}

public abstract double cost();

}

[/code]

[code]

package org.kangsg219.abst;

//调料(Condiment)抽象类

public abstract class CondimentDecorator extends Beverage {

public abstract String getDescription();

}

[/code]

[code]

package org.kangsg219.impl;

import org.kangsg219.abst.Beverage;

//浓缩咖啡(Espresso)具体类

public class Espresso extends Beverage {

public Espresso(){

description="Espresso";

}

@Override

public double cost() {

return 1.99;

}

}

[/code]

[code]

package org.kangsg219.impl;

import org.kangsg219.abst.Beverage;

//HouseBlend咖啡具体类

public class HouseBlend extends Beverage {

public HouseBlend(){

description="HouseBlend";

}

@Override

public double cost() {

return 0.89;

}

}

[/code]

[code]

package org.kangsg219.impl;

import org.kangsg219.abst.Beverage;

import org.kangsg219.abst.CondimentDecorator;

public class Mocha extends CondimentDecorator {

public Beverage beverage;

public Mocha(Beverage beverage){

this.beverage=beverage;

}

@Override

public String getDescription() {

return beverage.getDescription()+",mocha";

}

@Override

public double cost() {

return beverage.cost()+0.20;

}

}

[/code]

[code]

package org.kangsg219.impl;

import org.kangsg219.abst.Beverage;

import org.kangsg219.abst.CondimentDecorator;

//奶泡具体装饰类

public class Whip extends CondimentDecorator {

public Beverage beverage;

public Whip(Beverage beverage){

this.beverage=beverage;

}

@Override

public String getDescription() {

return beverage.getDescription()+",Whip";

}

@Override

public double cost() {

return beverage.cost()+ 0.10;

}

}

[/code]

[code]

package org.kangsg219.test;

import org.kangsg219.abst.Beverage;

import org.kangsg219.impl.Espresso;

import org.kangsg219.impl.HouseBlend;

import org.kangsg219.impl.Mocha;

import org.kangsg219.impl.Whip;

public class StarbuzzCoffee {

public static void main(String[] args) {

//仅要一杯浓缩咖啡，不要调料。

Beverage beverage=new Espresso();

System.out.println(beverage.getDescription()+" $"+beverage.cost());

//双倍摩卡的HouseBlend咖啡

Beverage beverage2=new HouseBlend();

beverage2=new Mocha(beverage2);

beverage2=new Mocha(beverage2);

beverage2=new Whip(beverage2);

System.out.println(beverage2.getDescription()+" $"+beverage2.cost());

}

}

[/code]

运行结果：

Espresso $1.99

HouseBlend,mocha,mocha,Whip $1.39