I think that is an old fashioned way of doing it. (very old fashioned may be)
You will have no more getters and setters. As Bibeault said, store them in a Map and then send that over to the set method. [set(map mP)].
Ah, the good old java.util.Calendar approach... The difference is, Calendar uses the same type for all values you can get using the fields. The only reason they have started using this approach is the number of methods you would get - I believe there are about 14 or so fields, so that would be 14 method sets with set, get, add and roll, giving you at least 56 methods. Ouch.
But for cases where the types differ or the number of methods would be relatively small, I strongly suggest not to use this approach.