为什么 ArrayList 有“实现列表"? [英] Why does ArrayList have "implements List"?

问题描述

在集合框架中，我们有接口 List 和类 AbstractList:

In the Collection Framework we have the interface List and the class AbstractList:

AbstractList implements List

和 ArrayList 扩展了 AbstractList 和

implements List

我的问题:为什么 ArrayList 有 implements List 子句?

My question: why does ArrayList have the implements List clause?

如果ArrayList继承了AbstractList，而AbstractList实现了List，那不是说ArrayList实现了List吗?

If ArrayList extends AbstractList and AbstractList implements List, can't we say, that ArrayList implement List?

推荐答案

是的.本来可以省略的.但是因此可以立即看出它是一个 List.否则需要额外点击代码/文档.我认为这就是原因 - 清晰.

Yes. It could've been omitted. But thus it is immediately visible that it is a List. Otherwise an extra click through the code / documentation would be required. I think that's the reason - clarity.

并添加 Joeri Hendrickx 评论的内容 - 这是为了表明 ArrayList 实现了 List.AbstractList 全图只是为了方便和减少 List 实现之间的代码重复.

And to add what Joeri Hendrickx commented - it is for the purpose of showing that ArrayList implements List. AbstractList in the whole picture is just for convenience and to reduce code duplication between List implementations.

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