[设计模式]装饰者模式(decorator)

//饮料超类
public abstract class Beverage{
    String description = "Unknown Beverage";
    public String getDescription(){
        return description;
    }

    public abstract double cost();
}

//饮料：深焙
public class DarkRoast extends Beverage{
    public DarkRoast(){
        description = "DarkRoast";
    }
    public double cost(){
        return .99;
    }
}

//饮料：低咖啡因
public class Decaf extends Beverage{
    public Decaf(){
        description = "Decaf";
    }
    public double cost(){
        return 1.05;
    }
}

//饮料：浓缩
public class Espresso extends Beverage{
    public Espresso(){
        description = "Espresso";
    }
    public double cost(){
        return 1.99;
    }
}

//饮料：综合
public class HouseBlend extends Beverage{
    public HouseBlend(){
        description = "House Blend coffee";
    }
    public double cost(){
        return .89;
    }
}

//调料都继承自这里
public abstract class CondimentDecorator extends Beverage{
    public abstract String getDescription();    
}

//调料：牛奶
public class Milk extends CondimentDecorator{
    Beverage beverage;
    public Milk(Beverage beverage){
        this.beverage = beverage;
    }
    public String getDescription(){
        return beverage.getDescription() + ",Milk";
    }
    public double cost(){
        return .10 + beverage.cost();
    }
}

//调料：摩卡
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();
    }
}

//调料：豆浆
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();
    }

//调料：奶泡
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();
    }
}

public class StarbuzzCoffee{
    public static void main(String args[]){
        Beverage beverage = new Espresso();
        System.out.println(beverage.getDescription() + " $" + beverage.cost());

        Beverage beverage2 = new DarkRoast();
        beverage2 = new Mocha(beverage2);
        beverage2 = new Mocha(beverage2);
        beverage2 = new Whip(beverage2);
        System.out.println(beverage2.getDescription() + " $" + beverage2.cost());

        Beverage beverage3 = new HouseBlend();
        beverage3 = new Soy(beverage3);
        beverage3 = new Mocha(beverage3);
        beverage3 = new Whip(beverage3);
        System.out.println(beverage3.getDescription() + " $" + beverage3.cost());

    }
}