That's incorrect in at least a couple of ways: rs.next() returns a boolean, and if having a null address is a normal condition, you wouldn't want to query on it or check if you didn't get any results--the issue (seems to be, anyway) that when the address value *is* null the original poster doesn't want "null" to show up for the user.
Option 1: Add a constraint to the column to not allow null and insert an empty string. There may be other reasons for allowing null, but if not needed then don't allow.
Option 2: Handle in UI. Use conditional statement Eg: (value==null) ? "" : value;