Binary search
nprivate int itemIndex (Student item,
n    StudentList list)
n The proper place for the specified item on the specified list, found using binary search.
n require:
n   list is sorted in increasing order
n  ensure:
n   0 <= result <= list.size()
n   for 0 <= i < result
n list.get(i) < item
n   for result <= i < list.size()
n list.get(i) >= item