而这就是为什么我承认类的原因：它们满足了自然世界系统的数学需要。

This, then, is why I recognize sets: to meet the mathematical needs of our system of the natural world.

youdao

注意：我必须承认，在这一点上我有些迷惑，既然api文档说IndexReader是一个抽象类(就是说它不能实例一个对象)。

NOTE: I have to admit, I'm a little confused at this point, since the API docs say IndexReader is abstract (which means it can't be instantiated).

youdao

我承认我没有系统地使用自动化测试，这是因为我的经验表明，对于那些其公共接口不经常更改的类，自动化测试是最有效的。

I confess that I do not use automated tests systematically because my experience has been that they are most effective with classes whose public interface does not change often.

youdao