How can I end a conversation and show I don’t want to talk to a guy.

Background info:

So this is my first year in college and there’s this guy that’s tried to ask me out on a date at school I let him know I was in a relationship and STILL every-time he sees me he tries to make small talk and I DON’T WANT TO TALK TO HIM!

Last time I was sitting in the library doing my work he walks up to me and says “hey how have you been” I looked up and said “I’m trying to focus on my work right now” and he walked away but seriously he’s acting like he knows me and I don’t like that!

Please tell me how you ladies how you would respond to these comments below in an assertive closed ended way, when you have no desire to talk to a person.

“What’s that’s your working on”?

“How was your class”?

“How’s your day going”?

“What’s your next class”?