在Java中实现通用接口 [英] Implementing Generic Interface in Java

问题描述

我有一个Java泛型问题，我希望有人可以回答。请考虑以下代码：

I have a Java generics question I was hoping someone could answer. Consider the following code:

public interface Event{}
public class AddressChanged implements Event{}
public class AddressDiscarded implements Event{}

public interface Handles<T extends Event>{
    public void handle(T event);
}

我想实现这样的Handles接口：

I want to implement this Handles interface like this:

public class AddressHandler implements Handles<AddressChanged>, Handles<AddressDiscarded>{
    public void handle(AddressChanged e){}
    public void handle(AddressDiscarded e){}
}

但是java不允许实现句柄两次使用通用。我能用C＃完成这个工作，但是不能在没有使用Reflection或instanceof和casting的情况下在java中找到解决方法。

But java doesn't allow implementing Handles twice using the Generic. I was able to accomplish this with C#, but cannot figure a workaround in java without using Reflection or instanceof and casting.

java是否有一种方法来实现Handles接口使用两个通用接口？或者也许另一种方式来编写句柄接口，以便最终结果可以完成？

Is there a way in java to implement the Handles interface using both generic interfaces? Or perhaps another way to write the Handles interface so the end result can be accomplished?

推荐答案

在Java中不能这样做。您只能实现同一个通用接口的一个具体实现。我会这样做：

You can't do that in Java. You can only implement one concrete realization of the same generic interface. I would do this instead:

public class AddressHandler implements Handles<Event>{
    public void handle(Event e){
      if(e instanceof AddressDiscarded){
         handleDiscarded(e);
      } else if(e instanceof AddressChanged){
         handleChanged(e);
      }
    }
    public void handleDiscarded(AddressDiscarded e){}
    public void handleChanged(AddressChanged e){}
}

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