如何在Java中扩展最终类 [英] How to extend a final class in Java

问题描述

这是我现在面临的问题。
我有一个类，假设 Foo ，这个类定义了一个名为 getBar 的方法，它返回一个 Bar 实例。类 Bar 在 Foo 中定义，并且声明为 public static final 。我想要做的是定义一个扩展 Foo 的类 MyFoo ，但我还要扩展通过添加我自己的功能（方法，属性等），使用 MyBar 栏。
我还希望 getBar 返回 MyBar 。

Here is my problem actually I'm facing now. I have a class, let's say Foo and this class defines a method called getBar that returns a Bar instance. The class Bar is defined inside Foo and and is declared public static final. What I want to do is to define a class MyFoo that extends Foo but I also want to extend Bar with MyBar by adding my own functionalities (methods, properties,etc). I also want getBar to return MyBar.

问题是 Bar 是最终的。以下是我想要做的事情的说明：

The problem is Bar is final. Here is an illustration of what I want to do :

public class Foo {

  Bar bar = new Bar();

  public Bar getBar(){
      return bar;
  } 

   ....

   public static final class Bar {

    } 
}

我想做的是：

public class MyFoo extends Foo {


   public MyBar getBar(){ // here I want to return an instance of MyBar

   }

  public static final class MyBar extends Bar { // That's impossible since Bar is final

  } 
}

我如何实现这一目标？

我在我的问题中添加了更多细节。
我实际上正在为Jenkins开发一个插件，在搜索之后，我发现有一个插件可以提供我想要的基本功能， Foo 和酒吧。我想自定义 Foo 和 Bar ，因此它可以满足我的需求。
Foo是插件的主要类，并扩展了一个名为Builder的类。 Foo定义了一个名为 perform 的方法，其中包含执行构建的所有操作。
Bar 包含用于配置目的的操作，Foo需要Bar来获取这些信息。

I am adding more details to my question. I am actually developing a plugin for Jenkins and after searching, I realize there is a plugin that offers the base functionalities that I want to do, Foo and Bar. I want to custom Foo and Bar, so it can fits my needs. Foo is the main class of the plugin and extends a class called Builder. Foo defines a method called perform which contains all the operations for performing a build. Bar contains operations for configurations purposes and Foo needs Bar to get those informations.

所以我想做的是用 MyFoo 扩展Foo并使用 MyBar 。如您所见， MyFoo 需要通过调用 getBar（）;

So what I want to do is to extend Foo with MyFoo and add some configurations with MyBar. And as you see, MyFoo will need to get those configuations by calling getBar();

第二件事是我无法控制 MyFoo 和 MyBar 的实例化

The second thing is I have no control of the instanciation of MyFoo and MyBar

阻止我的是，我无法扩展Bar。我怎样才能做到这一点？

What blocks me, is that I cannot extend Bar. How can I achieve that?

推荐答案

基本上你不能。看起来设计 Bar 的开发人员不打算扩展它 - 所以你不能扩展它。你需要寻找一个不同的设计 - 可能是一个不使用继承的设计......当然，假设你不能改变现有的代码。

You can't, basically. It looks like the developer who designed Bar intended for it not to be extended - so you can't extend it. You'll need to look for a different design - possibly one which doesn't use inheritance so much... assuming you can't change the existing code, of course.

（如果不了解更多关于这里的真正目标 - 整个系统的设计，很难给出更具体的建议。）

(It's hard to give more concrete advice without knowing more about the real goal here - the design of the overall system.)

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