I want to know how to handle something so that if it happens again I can deal with it, and hopefully avoid it anyway...

When I was in high school, (about 18), there was a lad in a few of my classes who I didn't like because he was so pompous and annoying... sometimes he would sit down in the chair next to me on purpose when there was nobody else in the room and hug me tight... from the side on. I don't like hugs in real life anyway and it scared me and I didn't know what to say to him or how to stop it because if I said 'Stop doing it' I had no way of enforcing what I said... he was taller than me and heavier and so my movement was restricted... I could only tell myself that it didn't mean anything because I'd heard rumours he was gay (never found out if that was true or not)... so I'd like to know if there is any way I could prevent this or anything similar from happening in the future...