装饰者模式（修饰者模式）

这里涉及到装饰者与被装饰者。所谓装饰者与被装饰者，就是被装饰者通过装饰者装饰，原有功能得到扩展，而本身代码不会发生变化。

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简单的理解就是在原有对象上包装一层附件动作，且保持包装完后的对象与被包装者属于同一个类族，但是额外附加了该包装类所特定的动作。

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首先定义一个抽象的类——>Drink，抽象出饮料的价格和名称：

public abstract class Drink {    public String name;    public double price;    public abstract double calcaTotalPrice();    public abstract String getAllName();    public Drink(){    }    public Drink(double price, String name) {        this.name = name;        this.price = price;    }    setter & getter ...}

接着定义一个被装饰者——>Coffee：

// 被装饰者public class Coffee extends Drink {    @Override    public double calcaTotalPrice() {        return this.price;    }    public Coffee() {    }       public Coffee(double price, String name) {        super(price, name);    }    public String getAllName() {        return this.getName();    }}

然后定义一个装饰者——Milk：

public class Milk extends Drink {    private Drink drink;    public Milk() {    }    public Milk(double price, String name, Drink drink) {        super(price, name);        this.drink = drink;    }    @Override    public double calcaTotalPrice() {        return this.price + this.drink.calcaTotalPrice();    }    @Override    public String getAllName() {        return this.getName() + " " + this.drink.getAllName();    }    public Drink getDrink() {        return drink;    }    public void setDrink(Drink drink) {        this.drink = drink;    }}

一图胜千言，同理，一句代码胜过一通乱**。测试类如下：

public class TestMain {    public static void main(String[] args) {        Coffee coffee = new Coffee(10, "咖啡");        System.err.println(coffee.calcaTotalPrice());        Milk milk = new Milk(5, "香蕉牛奶", coffee);        System.err.println(milk.calcaTotalPrice());        Milk milk1 = new Milk(3, "草莓牛奶", milk);        System.err.println(milk1.calcaTotalPrice());        System.err.println(milk1.getAllName());    }}

运行结果：10.015.018.0草莓牛奶 香蕉牛奶 咖啡