动态地给一个对象添加一些额外的职责，即增加其额外的功能。

package com.strife.pattern.decorator;

/**
 * 装饰器模式
 *
 * @author mengzhenghao
 * @date 2022/5/29
 */
public class Decorator {

    public static void main(String[] args) {
        AbstractDrink drink = new LongBlackCoffee();
        System.out.println(drink.getDesc() + " 价格：" + drink.cost());

        //加牛奶
        drink = new Milk(drink);
        System.out.println(drink.getDesc() + " 价格：" + drink.cost());

        //加糖
        drink = new Sugar(drink);
        System.out.println(drink.getDesc() + " 价格：" + drink.cost());

    }

}

/** 抽象主体 */
abstract class AbstractDrink {
    protected String desc;
    private float price = 0.0f;

    /** 计算费用的抽象方法 */
    abstract float cost();

    public String getDesc() {
        return desc;
    }

    public void setDesc(String desc) {
        this.desc = desc;
    }

    public float getPrice() {
        return price;
    }

    public void setPrice(float price) {
        this.price = price;
    }
}

/** 主体 */
class Coffee extends AbstractDrink {

    @Override
    float cost() {
        return super.getPrice();
    }
}

/** 意大利咖啡 */
class EspressoCoffee extends Coffee {

    public EspressoCoffee() {
        setDesc("意大利咖啡");
        setPrice(6.0f);
    }
}

/** 美式咖啡 */
class LongBlackCoffee extends Coffee {

    public LongBlackCoffee() {
        setDesc("美式咖啡 && 5.0");
        setPrice(5.0f);
    }
}

class ShortBlackCoffee extends Coffee {

    public ShortBlackCoffee() {
        setDesc("short black");
        setPrice(5.0f);
    }
}

/** 装饰者 */
class CoffeeDecorator extends AbstractDrink {

    private AbstractDrink drink;

    public CoffeeDecorator(AbstractDrink drink) {
        this.drink = drink;
    }

    @Override
    float cost() {
        return super.getPrice() + drink.cost();
    }

    @Override
    public String getDesc() {
        return drink.getDesc() + desc + " && " + super.getPrice();
    }
}

/** 具体的装饰者 */
class Milk extends CoffeeDecorator {

    public Milk(AbstractDrink drink) {
        super(drink);
        setDesc(" 加牛奶");
        setPrice(2.0f);
    }
}

/** 具体的装饰者 */
class Sugar extends CoffeeDecorator {

    public Sugar(AbstractDrink drink) {
        super(drink);
        setDesc(" 加糖");
        setPrice(1.0f);
    }
}