I've certainly written code that has this problem, I've tried to use my own code that has this problem, and good to us, right, good hygiene, I'm going to use that word again here, of getting into the habit of writing defensive code up front, it's part of that collection of things that you ought to do is a great thing to do.

我举手了吧？,我当然写过犯这种错误的程序了,我也尝试过应用含有这种错误的代码，不错，好的卫生，我还是要用这个词,对我们有帮助，养成写防卫性,代码的好习惯，是你应该做的,一系列事情之一,也是我们日后要做的主要的事情。

麻省理工公开课 - 计算机科学及编程导论课程节选