3. Update the record information, e.g. fill in the customer's ID. (using method of public void update(int recNo, String  data)).
4. Delete the record, i.e. make the mark the record as deleted, and should not be showed in other clients' GUI in the future (using the method of public void delete(int recNo)).
My second question is, since the requirment only say allow the user book a selected record, it doesn't say MUST allow user to return it, need I implement the Return function?
the user [...] CAN'T find the [modified] record in the search result [...] So what I can do is to write this limitation in the docment. Am I right?