设计模式之装饰模式

• 设计模式之装饰模式
• • 1. 作用
  • 2. 例子
  • 3. 装饰模式结构图
  • 4. java中的装饰模式

动态地给对象添加一些额外的功能，并且将所需的功能按照一定的顺序串联起来。

以奶茶加料计算价格为例，现在点一杯奶茶，茶底（2元），可以加的小料有珍珠（2元）、椰果（1元）、奶冻（3元）…

由此，我们可以写出的类结构如下
（个人觉得，在本例中，~milkyTea 那条线可以是组合也可以是依赖）

代码如下

package Decorator;


public abstract class MilkyTea {
    double price;

    public MilkyTea(double price) {
        this.price = price;
    }


    public double cost(){
        return 0;
    }
}

package Decorator;
package Decorator;


public class Tea extends MilkyTea{

    public Tea(){
        super(2);

    }

    @Override
    public double cost() {
        return this.price;
    }
}

package Decorator;


public abstract class SmallMaterial extends MilkyTea{
    MilkyTea milkyTea;

    public SmallMaterial(MilkyTea milkyTea) {
        super(milkyTea.price);
        this.milkyTea=milkyTea;
    }
}

package Decorator;


class Pearl extends SmallMaterial{

    public Pearl(MilkyTea milkyTea){
        super(milkyTea);
        this.price=2;
    }

    @Override
    public double cost() {
        return milkyTea.cost()+this.price;
    }
}


class NataDeCoco extends SmallMaterial{
    
    public NataDeCoco(MilkyTea milkyTea){
        super(milkyTea);
        this.price=1;
    }

    @Override
    public double cost() {
        return milkyTea.cost()+this.price;
    }
}


class Custard extends SmallMaterial{

    public Custard(MilkyTea milkyTea){
        super(milkyTea);
        this.price=3;
    }



    @Override
    public double cost() {
        return milkyTea.cost()+this.price;
    }
}

package Decorator;

public class Test {
    public static void main(String[] args) {
        MilkyTea milkyTea=new Tea();  //创建茶底对象

        MilkyTea pearl=new Pearl(milkyTea);  //珍珠（2元）+奶茶（2元）
        System.out.println(pearl.cost());  //4.0

        MilkyTea natadecoco=new NataDeCoco(pearl);  //珍珠（2元）+奶茶（2元）+椰果（1元）
        System.out.println(natadecoco.cost());  //5.0

        MilkyTea natadecoco2=new NataDeCoco(milkyTea);  //奶茶（2元）+椰果（1元）
        System.out.println(natadecoco2.cost());  //3.0

        MilkyTea custard = new Custard(natadecoco);  //珍珠（2元）+奶茶（2元）+椰果（1元）+奶冻（3元）
        System.out.println(custard.cost());  //8.0

    }
}

public abstract class InputStream implements Closeable {}

public class FilterInputStream extends InputStream {
    
    protected volatile InputStream in;
}

public class BufferedInputStream extends FilterInputStream {}

package Decorator;

import java.io.BufferedInputStream;
import java.io.FileInputStream;

public class Test {
    public static void main(String[] args) {
        try {
            FileInputStream fis = new FileInputStream("src/Decorator/a.txt");
            BufferedInputStream bif = new BufferedInputStream(fis);
            System.out.println(bif.read());

        } catch (Exception e) {
            e.printStackTrace();
        }
    }

}

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