Should university students be required to attend classes?

Should university students be required to attend classes? Some people believe that attending classes should be optional for students, but really disagree with them about it. In do not understand how university students can expect to learn much knowledge if thy do not attend classes. Although, self-study is a good way to acquire knowledge, I am of the opinion that no matter they like or not, university students should be required to attend classes because of following reasons.

In the first place, University students can acquire much knowledge when they attend classes. The professor can teach students a lot of things that are not written in the books. Books normal offer just concentrated knowledge. Therefore, the professor will clarify and expand knowledge; teach students the way of thinking, and the like. This expansion the students can not learn if they learn by themselves through the books. Sometimes, the professor can invite the guest speakers come to talk about some issues. They can have in common with students their experiences. Thus, by usually going to classes, university students can learn much knowledge that does not cover in textbook.
In the second place, attending classes, university students can learn more skills for their future life. In classes, the professor may require students to do teamwork. That means some students have to work together. As a result, they can learn some skills through their group assignment. They can learn how to deal with other people that their opinions are not the same. They have to their preparation to persuade others. They have to explain your ideas. This is communication skills. These skills are very important for students when they go to work in the future.
Moreover, going to classes can train university students to be more responsible and hard-working. Usually going to classes and keeping the schedule of classes require the effort of university students. That means they must learn their previous lessons at home and prepare for the next lesson. They have to arrange their time between attending classes and self-studying. If they want to be the best in their classes, they have to be responsible and hard-working and attending classes can train university students.
In conclusion, I think the university should require students to attend classes because the students can have much knowledge than they learn by themselves, learn more skills especial communication and team-work skill for their career in the future, and they will be responsible and hard-working. These are some advantages when students attend classes.