It's a common mistake to make if you forget that I've actually declared that variable up top, but wait a minute, I know any time that I use a variable, I have to declare it.

这是一个通常犯的错误，如果你忘了,之前在前面已经声明了这个变量，等等，我知道在任何时候,我使用一个变量，我必须声明它。

哈佛公开课 - 计算机科学课程节选

Initialization. A very common bug is to initialize a variable. Go through a loop, and then forget to reinitialize it when it needs to be reinitialized again.

忘记初始化,忘记初始化变量是一个很常见的错误,运行完一个循环之后,当需要再次初始化时。

麻省理工公开课 - 计算机科学及编程导论课程节选