如何在 Java 中扩展 final 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，比如说 Foo，这个类定义了一个名为 getBar 的方法，它返回一个 Bar 实例.Bar 类定义在 Foo 中，并声明为 public static final.我想要做的是定义一个扩展 Foo 的类 MyFoo 但我也想用 MyBar 扩展 Bar> 通过添加我自己的功能(方法、属性等).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.这是我想做的事情的说明:

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

  } 
}

我怎样才能做到这一点?

How can I achieve that?

我正在为我的问题添加更多细节.我实际上正在为 Jenkins 开发一个插件，经过搜索，我意识到有一个插件可以提供我想要做的基本功能，Foo 和 Bar.我想自定义 Foo 和 Bar，所以它可以满足我的需求.Foo 是插件的主类，并扩展了一个名为 Builder 的类.Foo 定义了一个名为 perform 的方法，它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 并用 MyBar 添加一些配置.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

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

阻碍我的是我无法扩展 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 的开发人员打算让它不被扩展 - 所以你不能扩展它.您需要寻找一种不同的设计——可能是一种不太使用继承的设计……当然，假设您无法更改现有代码.

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.

(如果不了解这里的真正目标 - 整个系统的设计，就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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