设计模式--装饰模式--案例分析

概述：装饰模式是一种对象结构型模型，动态地给一个对象增加一些额外的职责。就扩展功能而言，装饰模式提供了一种比使用子类对象更加灵活的替代方案实现：4个角色
(1)Component(抽象构件):
(2)ConcreteComponent(具体构件)
(3)Decorator(抽象装饰类)
(4)ConcreteDecorator(具体装饰类)

实例说明：某咖啡店在卖咖啡时可以根据顾客的要求在其中加入各种配料，咖啡店会根据所加入的配料来计算总费用。现使用装饰模式为该咖啡店设计一个程序以实现计算费用的功能，输出每种饮料的详细描述及花费。

package com.design.DecoratorMode;

public abstract class Beverage {
    public abstract String getDescription();

    public abstract double getCost();
}

package com.design.DecoratorMode;

public class Espresso extends Beverage{
    @Override
    public String getDescription() {
        return "Espresso 咖啡";
    }

    @Override
    public double getCost() {
        return 25;
    }
}

package com.design.DecoratorMode;

public class CondimentDecorator extends Beverage{
    private Beverage beverage;

    public CondimentDecorator(Beverage beverage) {
        this.beverage = beverage;
    }

    @Override
    public String getDescription() {
        return beverage.getDescription();
    }

    @Override
    public double getCost() {
        return beverage.getCost();
    }
}

package com.design.DecoratorMode;

public class Milk extends CondimentDecorator{

    public Milk(Beverage beverage) {
        super(beverage);
    }

    public String getDescription(){
        return super.getDescription() + this.addMilk();
    }

    public double getCost(){
        return super.getCost()+this.addMilkCost();
    }

//    新增业务方法
    public String addMilk(){
        return "加牛奶";
    }

    public double addMilkCost(){
        return 6;
    }
}

package com.design.DecoratorMode;

public class Mocha extends CondimentDecorator{
    public Mocha(Beverage beverage) {
        super(beverage);
    }

    public String getDescription(){
        return super.getDescription() + this.addMocha();
    }

    public double getCost(){
        return super.getCost() + this.addMochaCost();
    }

    private double addMochaCost() {
        return 10;
    }

    private String addMocha() {
        return "加摩卡";
    }
}

package com.design.DecoratorMode;


public class StarBuzzCoffee {
    public static void main(String[] args) {
        Beverage b1, b2, b3;

        b1 = new Espresso();
//        这里交给大家补充一个HouseBlend类
//        b1 = new HouseBlend();
        System.out.println("饮料：" + b1.getDescription());
        System.out.println("价格：" + b1.getCost());
        System.out.println("----------------------------");


        b2 = new Milk(b1);
        System.out.println("饮料：" + b2.getDescription());
        System.out.println("价格：" + b2.getCost());
        System.out.println("----------------------------");

        b3 = new Mocha(b2);
        System.out.println("饮料：" + b3.getDescription());
        System.out.println("价格：" + b3.getCost());
        System.out.println("----------------------------");
    }
}