Why doesnt this guy ever say hi to me when he knows me? instead he hugs my friend?

We have seen eachother around and I have said hi to him once but whenever im with my friend he comes and hugs her and taks to her and dances with her and its like im invisible or something...i dont know why the heck he does this but its rude. I dont like this guy i was just wondering why he doesnt say hi to me ever....like he acts as if i dont exist