Java中的多态性和接口(可以使用多态来实现接口……为什么？)

下面是“Observer”模式的具体示例,使用类和接口在记录器系统中完成多态行为：

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：

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.