Java中的多态性和接口（可以使用多态来实现接口......为什么？） [英] Polymorphism and Interfaces in Java (can polymorphism be used to implement interfaces...why?)

问题描述

在现实世界中，人们使用它来解决什么类型的问题？我可以看到这些协同工作的示例代码吗？我能找到的只是关于猫狗说话或喝牛奶或咖啡的人的代码...

In the real world what do people use this for (to solve what types of problems)? Can I see some example code of these working together? All I can find is code about cats and dogs speaking or people drinking milk or coffee...

人们真的用接口实现多态吗？为什么？

Do people really implement polymorphism with interfaces? What for?

推荐答案

当然，

下面是具体的例子观察者模式，使用类和接口在记录器系统中完成多态行为：

Below is concrete example of the "Observer" pattern, using classes and interfaces to accomplish polymorphic behavior in a logger system:

interface ILogger{

   public void handleEvent (String event);
}

class FileLogger implements ILogger{

   public void handleEvent (String event){
       //write to file
   }
}

class ConsoleLogger implements ILogger{

   public void handleEvent (String event){
       System.out.println( event );
   }
}

class Log {

   public void registerLogger (ILogger logger){

       listeners.add(logger);
   }

   public void log (String event){

       foreach (ILogger logger in listeners){

            logger.handleEvent(event); //pass the log string to both ConsoleLogger and FileLogger!
       }
   }

   private ArrayList<ILogger> listeners;
}

然后，您可以按如下方式使用它：

Then, you could use it as follows:

public static void main(String [] args){

     Log myLog();
     FileLogger myFile();
     ConsoleLogger myConsole();

     myLog.registerLogger( myFile );    
     myLog.registerLogger( myConsole );

    myLog.log("Hello World!!");
    myLog.log("Second log event!");
}

希望这有助于您理解接口和多态性。

Hope this helps your understanding of interfaces and polymorphism.

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