Hi Alexandra,
The best way to handle this is : consider customer id as
String of length 8 (just check if this is not breaking any requirements).
I internally used a record number (for locking/unlocking record) which was an 'int' (meaning my code will not support data file with more than 32767 records, and I did mention this in choices.txt), but my requirement said that owner id must be 8 digit long (but did not explicitly mention any data-type).
Just think about it : why do you want to treat customer id as 'number'? Are you doing any 'numerical' operations on it? I don't think so. All you'll be doing is - add a new record, delete a record and so on.
So, I would strongly recommend to treat customer id as String, and make very sure to add a validation at UI level that user can enter only numerical data there (and that too, max 8 characters long).
Hope this helps.
All the best!
Regards,
Anayonkar Shivalkar (SCJP, SCWCD, OCMJD, OCEEJBD)