设计模式6之（装饰者模式）

观察者模式（设计模式）

若有不恰之处，请各位道友指正~

个人觉得，看懂类图就是学习设计模式的精髓了。

策略模式概念

• 动态地将责任链附加到对象上，若要拓展功能，装饰者提供了比继承更有弹性的替代方案

根据类图写代码
代码结构

//饮料
public abstract class Beverage {

    public String description = "unknown beverage";

    public String describle(){
        return description;
    }

    public abstract double cost();
}

//佐料
public abstract class CondimentDecorator extends Beverage{

    @Override
    public abstract String describle();
}

//佐料（牛奶）
public class Milk extends CondimentDecorator{

    Beverage beverage;

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

    @Override
    public String describle(){
        return beverage.describle() + "Milk";
    }

    @Override
    public double cost() {
        return 0.29 + beverage.cost();
    }
}

//佐料（摩卡）
public class Mocha extends CondimentDecorator {

    Beverage beverage;

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

    @Override
    public String describle(){
        return beverage.describle() + "Mocha";
    }

    @Override
    public double cost() {
        return beverage.cost() + 0.99;
    }
}

//浓缩咖啡
public class Espresso extends Beverage {

    public Espresso(){
        description = "Espresso";
    }

    @Override
    public double cost() {
        return 1.69;
    }
}

//test
public class Test {

    public static void main(String[] args) {

        Beverage beverage = new Espresso();
        beverage = new Mocha(beverage);
        beverage = new Milk(beverage);
        String description = beverage.describle();
        System.out.println(beverage.cost() + "------"+description);


    }
}

不过该设计模式还是要组合工厂模式一起使用，能发挥强大的魅力~