Is this normal for a young guy?

Is it normal to get an erection as soon as i speak to an attractive girl?? I spoke to a girl i like in the canteen line and "barred up" just at the sight of her, i found it very embarrasing. how will i react to her tommorrow when i see her???? i tried to shove it under my jeans band but i couldn't in time, it ******* sucks!