Introduction to iterator pattern of Java design pattern

After so many years of study, I found a problem. It seems that teachers like roll call very much, and even roll call has become a hobby of some teachers. If you don't roll call for a day, you can't eat well and sleep well. I think it's very strange. If you speak well in your class, how can students not come to the class? I don't know: "it's a crime to mislead people's children!" Ah.

Well, let's now look at how the teacher roll call process is implemented: 1. According to the old rule, let's first define the teacher interface class: