How did he know my name??

okay so lets just say theres this guy named bob..okay i have a crush on bob..but ive never talked to bob. we had a spanish class together last year but in spanish we dont use our real names..anyways i believe he has a crush on me too but im not sure..anyways we start school in september..and im hoping we have a class together..and if we do im planning on trying to become friends with him..but my question is how do i start the conversation..do i say ';hey bob, whats up'; or do i pretend like i dont know his first name and be like ';hey whats up? whats your name?'; i would use the other approach but i dont want the ';how did she know my name'; question to pop up becuase if he doesnt like me that would we be embarassing...but im not sure which way do i approach? thank you sooo much for the help. :]How did he know my name??
be all flirty and say ';uhhh your bob rite? im .......';How did he know my name??
If you know his name......then use it.
ummmm use his real name. He will think it's cool that you know who he is and it will let him know that he can say your name too.
just say

';hey your names bob right?';

so you sound kinda unsure and then compliment something on him..

shirt etc.