我应该扩展ArrayList（is-a）还是应该将其作为成员包含（has-a）？ [英] Should I extend an ArrayList (is-a) or should I include it as a member (has-a)?

问题描述

我正在制作一个维护数字列表的简单程序，我希望这个列表也有一个名字。哪种方法最好：让我的列表类扩展ArrayList还是让它包含一个ArrayList成员？在这两种情况下，当然都会有一个名称字符串成员。

I'm making a simple program that maintains a list of numbers, and I want this list to also have a name. Which is the best approach: have my list class extend ArrayList or have it include an ArrayList member? In both cases, there would of course be a "name" String member.

第一种方法意味着我只需要实现一个getter&这个名字的setter，但我认为这会使我的课程与特定的实现过于紧密联系？例如，如果我想稍后使用Vector，那么我必须在任何地方更改代码。

The first approach means I only have to implement a getter & setter for the name, but I think this would tie my class too closely to a particular implementation? For example, if I wanted to later use a Vector, than I would have to change code everywhere.

第二种方法可以更容易地更改实现，但是当然，因为我必须实现一堆包装器，所以当然变得非常讨厌。

The second approach would make it easier to change the implementation, but of course becomes quite annoying for now, since I have to implement a bunch of wrappers.

我已经阅读了关于继承与组合的SO帖子，因为我的列表是一种ArrayList，我倾向于第一种方法。但是，讨论是否存在任何差异，因为我正在扩展Collection类vs扩展通用类？或者我是否过度思考？

I've read the SO posts regarding inheritance vs. composition, and since my list is a type of ArrayList, I am leaning towards the first approach. However, is there any differences to the discussion because I'm extending a Collection class vs extending a general class? Or am I over-thinking this?

推荐答案

两者都不是更好，这是你提到的权衡。

Neither is better, its a trade-off as you mentioned.

如果你进行聚合（has-a），你必须包含你将要使用的成员的所有功能（即实现调用它们的函数）

If you do aggregation (has-a) you have to wrap all the functionality of the member you're going to use (i.e implement functions that call them)

如果你继承了，很多函数都会添加到你的新类中，这可能是不必要的，你也需要实现抽象函数。

If you do inheritance, A lot of functions are added to your new class which might be unneccessary, And you need to implement abstract functions as well.

如果您在C ++环境中，私有继承将是一个选项，但这里有利有弊

If you were in a C++ environment, private inheritance would be an option, But here both have pros and cons

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