Hi Daniel,
First of all: why would you need a map to sort the rooms by room number (recNo)? I don't think a CSR is interested in a recNo, I guess they would be more interested in a sort on name and/or location. I simply used a List to store the rooms and that's it. If in a next release a request to sort the records is asked, I will implement a TableRowSorter for example. But now that's not needed, so simple don't do it.
Here you can read some details about my approach with the List.
Kind regards,
Roel