It's a bad habit to get into, because when you come back to it, it may haunt you later on down the road. So really get into that notion of trying to be defensive as you program.

来运行程序的时候,错误就会出现缠住你了,因此现在我们真的要培养,在程序中有防卫性设计的概念。

麻省理工公开课 - 计算机科学及编程导论课程节选