What that method does is add all the items in the datalist to the polist.
What you seem to want is to add the datalist to the polist (ie end up with a list of lists)
in which case what you want is:
I would echos Bear's comments about java code in JSPs.
I would also suggest you come up with a better structure than a List of Lists.
Why not create a java bean to represent what you want, and return a list of them?