Java设计模式（装饰者模式）

装饰者模式

在不修改任何底层代码的情况下，给你的（或别人的）对象赋予新的职责。
设计原则：

1. 类应该对扩展开放，对修改关闭。

实体类

/*** 饮料** @author NNroc* @date 2020/8/4 11:36*/
public abstract class Beverage {protected String description = "Unknown Beverage";public String getDescription() {return description;}public abstract double cost();
}


/*** 调料* CondimentDecorator 取代 Beverage** @author NNroc* @date 2020/8/4 11:48*/
public abstract class CondimentDecorator extends Beverage {public abstract String getDescription();
}


实现类（咖啡种类 Beverage）

/*** 深焙** @author NNroc* @date 2020/8/4 12:00*/
public class DarkRoast extends Beverage {public DarkRoast() {description = "Dark Roast Coffee";}public double cost() {return .99;}
}


/*** 低咖啡因** @author NNroc* @date 2020/8/4 12:02*/
public class Decat extends Beverage {public Decat() {description = "Decat Coffee";}public double cost() {return 1.05;}
}


/*** 浓缩咖啡** @author NNroc* @date 2020/8/4 11:51*/
public class Espresso extends Beverage {public Espresso() {description = "Espresso";}public double cost() {return 1.99;}
}


/*** 综合** @author NNroc* @date 2020/8/4 11:53*/
public class HouseBlend extends Beverage {public HouseBlend() {description = "House Blend Coffee";}public double cost() {return .89;}
}


实现类（配料 CondimentDecorator）

/*** 摩卡** @author NNroc* @date 2020/8/4 11:55*/
public class Mocha extends CondimentDecorator {Beverage beverage;public Mocha(Beverage beverage) {this.beverage = beverage;}public String getDescription() {return beverage.getDescription() + ", Mocha";}public double cost() {return .20 + beverage.cost();}
}


/*** 豆浆** @author NNroc* @date 2020/8/4 12:03*/
public class Soy extends CondimentDecorator {Beverage beverage;public Soy(Beverage beverage) {this.beverage = beverage;}public String getDescription() {return beverage.getDescription() + ", Soy";}public double cost() {return .15 + beverage.cost();}
}


/*** 奶油** @author NNroc* @date 2020/8/4 12:04*/
public class Whip extends CondimentDecorator {Beverage beverage;public Whip(Beverage beverage) {this.beverage = beverage;}public String getDescription() {return beverage.getDescription() + ", Whip";}public double cost() {return .10 + beverage.cost();}
}


测试

/*** @author NNroc* @date 2020/8/4 11:58*/
public class StarbuzzCoffee {public static void main(String[] args) {// 不加配料的 EspressoBeverage beverage = new Espresso();System.out.println(beverage.getDescription() + " $" + beverage.cost());// 加3个配料的 DarkRoastBeverage beverage2 = new DarkRoast();beverage2 = new Mocha(beverage2);beverage2 = new Mocha(beverage2);beverage2 = new Whip(beverage2);System.out.println(beverage2.getDescription() + " $" + beverage2.cost());// 加3个不同配料的 HouseBlendBeverage beverage3 = new HouseBlend();beverage3 = new Soy(beverage3);beverage3 = new Mocha(beverage3);beverage3 = new Whip(beverage3);System.out.println(beverage3.getDescription() + " $" + beverage3.cost());}
}