装饰模式

Posted on | In |

装饰模式要达到的目的：装饰模式指的是在不必改变原类文件和使用继承的情况下，动态地扩展一个对象的功能。它是通过创建一个包装对象，也就是装饰来包裹真实的对象。

1.类图


2.具体实例

2.1 Application


package Decorator;
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/**
 * Created by 15581 on 2017/11/8.
 */ // Observer.Application.java
public class Application{
   public void needBird(Bird bird){
       int flyDistance=bird.fly();
       System.out.println("这只鸟能飞行"+flyDistance+"米");
   }
   public static void main(String args[]){
      Application client=new Application();
      Sparrow sparrow=new Sparrow();
      SparrowDecorator sparrowDecorator1=
      new SparrowDecorator(sparrow);
      SparrowDecorator sparrowDecorator2=
      new SparrowDecorator(sparrowDecorator1);
      client.needBird(sparrowDecorator1);
      client.needBird(sparrowDecorator2);
  }
}

2.2 Bird


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package Decorator;

// Bird.java
public abstract class Bird{
   public abstract int fly();
}

2.3 Decorator


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package Decorator;

/**
 * Created by 15581 on 2017/11/8.
 */ // Decorator.java
public abstract class  Decorator extends Bird{
    protected Bird bird;
    public Decorator(){
    }
    public Decorator(Bird bird){
       this.bird=bird;
    }
}

2.4 Sparrow


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package Decorator;

/**
 * Created by 15581 on 2017/11/8.
 */ // Sparrow.java
public class Sparrow extends Bird{
   public final int DISTANCE=100;
   public int fly(){
      return DISTANCE;
   }
}

2.5 SparrowDecorator


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package Decorator;

/**
 * Created by 15581 on 2017/11/8.
 */ // SparrowDecorator.java
public class  SparrowDecorator extends Decorator{
   public final int DISTANCE=50;        //eleFly方法能飞米
   SparrowDecorator(Bird bird){
      super(bird);
   }
   public int fly(){
      int distance=0;
      distance=bird.fly()+eleFly();  //委托被装饰者bird调用fly()，然后再调用eleFly()
      return distance;
   }
   private int eleFly(){              //装饰者新添加的方法
      return DISTANCE;
   }
}

2.6 SparrowDecoratorTwo


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package Decorator;

/**
 * Created by 15581 on 2017/11/8.
 */ // SparrowDecoratorTwo.java
public class  SparrowDecoratorTwo extends Decorator{
   public final int DISTANCE=20;
   SparrowDecoratorTwo(Bird bird){
      super(bird);
   }
   public int fly(){
      int distance=0;
      distance=bird.fly()+eleFly();
      return distance;
   }
   public int eleFly(){
      return DISTANCE;
   }
}