结构型模式————装饰器模式(3.1)

  • 2019 年 10 月 3 日
  • 筆記

什么是装饰器模式?

【先吃三颗栗子:】

1.PC=主机+显示器+键盘+鼠标+鼠标垫

主机是核心,而其他的组成部分都是装饰。

2.手抓饼=+鸡蛋+培根+黄瓜

饼是核心,鸡蛋,培根是可选的,可以理解为装饰。

3.咖啡=咖啡+牛奶+冰+方糖

咖啡是核心,牛奶等可选。

比喻虽然形象生动,但是与实际或多或少会产生偏差。

抽象的解释:装饰器模式的目的——核心部分和装饰部分可以自由组合。

装饰器模式的功能

对于软件开发来说,聚焦于软件的灵活性和可扩展性。

装饰器模式要求:

  • 装饰可选
  • 装饰可扩展
  • 核心部分可扩展

手抓饼中的装饰器模式

实现饼加各种配料的价格计算。

思路:

1.定义抽象类手抓饼,其中包含获取种类的抽象方法和获取价格的抽象方法。

2.然后定义两个分别为大份手抓饼和中份手抓饼来继承这个抽象类,重写两个方法定义种类和价格。

3.定义具体的配料类继承手抓饼抽象类,先定义构造器传入已经创建的手抓饼种类,然后重写种类和价格方法。

在网上看的一些博客,是创建出一个抽象的配料类来继承抽象产品类,然后用具体的配料类来实现抽象配料类,实现装饰。

可是如果直接将抽象产品类的方法全部定义抽象方法,配料类直接继承重写,实现装饰,功能上也是可以实现的,如下所示,Bacon类直接继承HandPancake,然后重写getName和getCost方法,实现装饰。似乎也没有问题:

但是设计模式毕竟是一种经验总结,如果有已经看出端倪的小伙伴们在下方留言交流一下吧!

直接继承HandPancake

abstract class HandPancake  {      public abstract String getName();        public abstract int getCost();  }    class HandPancake_Big extends HandPancake  {      @Override      public String getName() {          return "大份手抓饼";      }        @Override      public int getCost() {          return 10;      }  }    class HandPancake_Mid extends HandPancake  {      @Override      public String getName() {          return "中份手抓饼";      }        @Override      public int getCost() {          return 8;      }  }  class Bacon extends HandPancake  {      private HandPancake handPancake;        Bacon(HandPancake handPancake)      {          this.handPancake=handPancake;      }        @Override      public String getName() {          return handPancake.getName()+"加培根";      }        @Override      public int getCost() {          return handPancake.getCost()+1;      }  }  class Cucumber extends HandPancake  {      private HandPancake handPancake;        Cucumber(HandPancake handPancake)      {          this.handPancake=handPancake;      }        @Override      public String getName() {          return handPancake.getName()+"加黄瓜";      }        @Override      public int getCost() {          return handPancake.getCost()+2;      }  }  class Ham extends HandPancake  {      private HandPancake handPancake;        Ham(HandPancake handPancake)      {          this.handPancake=handPancake;      }        @Override      public String getName() {          return handPancake.getName()+"加火腿";      }        @Override      public int getCost() {          return handPancake.getCost()+1;      }  }      public class APPlication  {      public static void main(String[] args) {          HandPancake handPancake_big = new HandPancake_Big();            System.out.println("啥也不加"+handPancake_big.getName()+":"+handPancake_big.getCost());            handPancake_big = new Ham(handPancake_big);            System.out.println(handPancake_big.getName()+":"+handPancake_big.getCost());            handPancake_big = new Cucumber(handPancake_big);            System.out.println(handPancake_big.getName()+":"+handPancake_big.getCost());            handPancake_big = new Bacon(handPancake_big);            System.out.println(handPancake_big.getName()+":"+handPancake_big.getCost());            System.out.println("==============================");          HandPancake handPancake_mid = new HandPancake_Mid();          System.out.println("啥也不加"+handPancake_mid.getName()+":"+handPancake_mid.getCost());            handPancake_mid = new Ham(handPancake_mid);            System.out.println(handPancake_mid.getName()+":"+handPancake_mid.getCost());            handPancake_mid = new Cucumber(handPancake_mid);            System.out.println(handPancake_mid.getName()+":"+handPancake_mid.getCost());            handPancake_mid = new Bacon(handPancake_mid);            System.out.println(handPancake_mid.getName()+":"+handPancake_mid.getCost());          }  }

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官方做法:

abstract class HandPancake  {      String name;                      //1      public  String getName()      {          return name;      }        public abstract int getCost();  }    class HandPancake_Big extends HandPancake  {      HandPancake_Big()         //2.通过构造器赋值      {          name="大份手抓饼";      }          @Override      public int getCost() {          return 10;      }  }    class HandPancake_Mid extends HandPancake  {      HandPancake_Mid()         //2.通过构造器赋值      {          name="中份手抓饼";      }          @Override      public int getCost() {          return 8;      }  }    abstract class Condiments  extends HandPancake   //3.定义抽象接口  {      public abstract String getName();  }    class Bacon extends Condiments     //4.继承抽象接口  {      private HandPancake handPancake;        Bacon(HandPancake handPancake)      {          this.handPancake=handPancake;      }        @Override      public String getName() {          return handPancake.getName()+"加培根";      }        @Override      public int getCost() {          return handPancake.getCost()+1;      }  }  class Cucumber extends Condiments  {      private HandPancake handPancake;        Cucumber(HandPancake handPancake)      {          this.handPancake=handPancake;      }        @Override      public String getName() {          return handPancake.getName()+"加黄瓜";      }        @Override      public int getCost() {          return handPancake.getCost()+2;      }  }  class Ham extends Condiments  {      private HandPancake handPancake;        Ham(HandPancake handPancake)      {          this.handPancake=handPancake;      }        @Override      public String getName() {          return handPancake.getName()+"加火腿";      }        @Override      public int getCost() {          return handPancake.getCost()+1;      }  }      public class APPlication  {      public static void main(String[] args) {          HandPancake handPancake_big = new HandPancake_Big();            System.out.println("啥也不加"+handPancake_big.getName()+":"+handPancake_big.getCost());            handPancake_big = new Ham(handPancake_big);            System.out.println(handPancake_big.getName()+":"+handPancake_big.getCost());            handPancake_big = new Cucumber(handPancake_big);            System.out.println(handPancake_big.getName()+":"+handPancake_big.getCost());            handPancake_big = new Bacon(handPancake_big);            System.out.println(handPancake_big.getName()+":"+handPancake_big.getCost());            System.out.println("==============================");          HandPancake handPancake_mid = new HandPancake_Mid();          System.out.println("啥也不加"+handPancake_mid.getName()+":"+handPancake_mid.getCost());            handPancake_mid = new Ham(handPancake_mid);            System.out.println(handPancake_mid.getName()+":"+handPancake_mid.getCost());            handPancake_mid = new Cucumber(handPancake_mid);            System.out.println(handPancake_mid.getName()+":"+handPancake_mid.getCost());            handPancake_mid = new Bacon(handPancake_mid);            System.out.println(handPancake_mid.getName()+":"+handPancake_mid.getCost());          }  }

1565696715504

手抓饼的扩展性

  • 创建手抓饼的种类
  • 创建配料种类

官方的扩展:创建一个小份手抓饼继承Hanpancake,然后创建配料继承Condiments。

贴一下直接继承HandPancake的情况:

class HandPancake_Smalll extends HandPancake
class Egg extends HandPancake

abstract class HandPancake  {      public abstract String getName();        public abstract int getCost();  }    class HandPancake_Big extends HandPancake  {      @Override      public String getName() {          return "大份手抓饼";      }        @Override      public int getCost() {          return 10;      }  }    class HandPancake_Mid extends HandPancake  {      @Override      public String getName() {          return "中份手抓饼";      }        @Override      public int getCost() {          return 8;      }  }  class Bacon extends HandPancake  {      private HandPancake handPancake;        Bacon(HandPancake handPancake)      {          this.handPancake=handPancake;      }        @Override      public String getName() {          return handPancake.getName()+"加培根";      }        @Override      public int getCost() {          return handPancake.getCost()+1;      }  }  class Cucumber extends HandPancake  {      private HandPancake handPancake;        Cucumber(HandPancake handPancake)      {          this.handPancake=handPancake;      }        @Override      public String getName() {          return handPancake.getName()+"加黄瓜";      }        @Override      public int getCost() {          return handPancake.getCost()+2;      }  }  class Ham extends HandPancake  {      private HandPancake handPancake;        Ham(HandPancake handPancake)      {          this.handPancake=handPancake;      }        @Override      public String getName() {          return handPancake.getName()+"加火腿";      }        @Override      public int getCost() {          return handPancake.getCost()+1;      }  }  //========================    class HandPancake_Smalll extends HandPancake  {      @Override      public String getName() {          return "小份手抓饼";      }        @Override      public int getCost() {          return 5;      }  }      class Egg extends HandPancake  {      private HandPancake handPancake;        Egg(HandPancake handPancake)      {          this.handPancake=handPancake;      }        @Override      public String getName() {          return handPancake.getName()+"加鸡蛋";      }        @Override      public int getCost() {          return handPancake.getCost()+1;      }  }      public class APPlication  {      public static void main(String[] args) {          HandPancake handPancake_big = new HandPancake_Big();            System.out.println("啥也不加"+handPancake_big.getName()+":"+handPancake_big.getCost());            handPancake_big = new Ham(handPancake_big);            System.out.println(handPancake_big.getName()+":"+handPancake_big.getCost());            handPancake_big = new Cucumber(handPancake_big);            System.out.println(handPancake_big.getName()+":"+handPancake_big.getCost());            handPancake_big = new Bacon(handPancake_big);            System.out.println(handPancake_big.getName()+":"+handPancake_big.getCost());            System.out.println("==============================");          HandPancake handPancake_mid = new HandPancake_Mid();          System.out.println("啥也不加"+handPancake_mid.getName()+":"+handPancake_mid.getCost());            handPancake_mid = new Ham(handPancake_mid);            System.out.println(handPancake_mid.getName()+":"+handPancake_mid.getCost());            handPancake_mid = new Cucumber(handPancake_mid);            System.out.println(handPancake_mid.getName()+":"+handPancake_mid.getCost());            handPancake_mid = new Bacon(handPancake_mid);            System.out.println(handPancake_mid.getName()+":"+handPancake_mid.getCost());              System.out.println("扩展性测试:");            HandPancake handPancake_small = new HandPancake_Smalll();          System.out.println("啥也不加"+handPancake_small.getName()+":"+handPancake_small.getCost());            handPancake_small = new Egg(handPancake_small);            System.out.println(handPancake_small.getName()+":"+handPancake_small.getCost());                  }  }

运行结果:

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