It ultimately evaluates that line of code but just once the stuff inside the curly braces, but the semicolon on the end, essentially has the effect of this.

它最终执行了那行代码,但是只有一次，当那个东西在花括号里，分号放在后面，本质上影响了这个循环。

哈佛公开课 - 计算机科学课程节选