Random people generator in java [on hold]

hi i want to develop a small application for college in which we required the no of people during final examination.there are 30 people availabe with us. there is a examination last for 40 days. at each days i required some people from out of 30 for block supervision.(e.g. 7 people). so these required number of people is automatically generated each day such that each people get equal number of chance at the end of 40 days. can anybody give me some suggesstion how can i implement this???