设计模式学习 装饰模式

装饰模式概念如下：

使用动机

简单例子

假设一个快餐，比如炒饭。但是可以添加小菜(鸡蛋,培根)

定义快餐类(定义cost接口)

public abstract class FastFood {
    private float price;
    private String desc;
    public FastFood() {
    }
    public FastFood(float price, String desc) {
        this.price = price;
        this.desc = desc;
    }

    public float getPrice() {
        return price;
    }

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

    public String getDesc() {
        return desc;
    }

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

定义炒饭(可以被额外装饰的类)

public class FiledRice extends FastFood {
    public FiledRice(){
        super(10,"炒饭");
    }
    @Override
    public float cost() {
        return getPrice();
    }
}

定义装饰抽象类（所有具体的装饰类继承它）

//装饰类
public abstract class Garnish extends FastFood{
    private FastFood fastFood;
    public FastFood getFastFood(){
        return fastFood;
    }
    public void setFastFood(FastFood fastFood){
        this.fastFood=fastFood;
    }
    public Garnish(FastFood fastFood, float price, String desc){
        super(price, desc);
        this.fastFood=fastFood;
    }
}

定义培根(可以附加上去的功能)

public class Bacon extends Garnish {
    public Bacon(FastFood fastFood) {
        super(fastFood, 2,"培根");
    }

    @Override
    public float cost() {
        return getPrice()+getFastFood().getPrice();
    }
    public String getDesc(){
        return super.getDesc()+getFastFood().getDesc();
    }
}

同理定义鸡蛋

public class Egg extends Garnish {
    public Egg(FastFood fastFood) {
        super(fastFood, 2, "鸡蛋");
    }

    @Override
    public float cost() {
        return getPrice()+getFastFood().getPrice();
    }
    public String getDesc(){
        return super.getDesc()+getFastFood().getDesc();
    }
}

主程序

public class Client {
    public static void main(String[] args) {
        //点一份炒饭
        FastFood food=new FiledRice();
        //花费的价格
        System.out.println(food.getDesc()+" "+food.cost()+"元");
        System.out.println("-------");
        //点一份鸡蛋抄饭
        FastFood food1=new FiledRice();
        food1=new Egg(food1);
        //花费的价格
        System.out.println(food1.getDesc()+" "+food1.cost()+"元");
        //点一份培根鸡蛋饭
        food1=new Bacon(food1);
        //花费的价格
        System.out.println(food1.getDesc()+" "+food1.cost()+"元");
    }
}

总结