Is my approach to this problem correct?

Question

Hi, I'm new to Java and OO programming, and this is my first coding experience
in Java, so, be patient...!
I'd like to know if the approach I'm adopting for the following exercise is
acceptable. Hints and critics on how could I improve it are the reason for this
post, I don't want you make my homeworks ;-)
The exercise asks to realize a simple list of telephone numbers containing
namesurname/telephonenumber couples (namesurnames are unique). The
list must be saved permanently on the disk, the user may be able to search a number
providing a name, to add a new record, to remove and modify an existing record.
Finally, it can be possible to load different data files. All these operations
must be available via GUI.
I still don't know how to create GUIs, so I thought that as a first step it
could be a good move to develop the set of API to
save/load/search/add/remove/change, and once these API work fine, create a GUI
that uses these API.
I have identified just one class that models this problem: the class that
represents the whole set of names and telephone numbers, and I'd like to use it
in this manner:
nameNumsList.search("namesurname");
nameNumsList.insert("namesurname", "number");
nameNumsList.remove("namesurname");
nameNumsList.change("namesurname", "number");
nameNumsList.load("filename");
nameNumsList.save("filename");
To handle data persistence, I will store each item (one item for line) in a
file, in this form: namesurname;number.
To load data from file to memory I have been attracted to java.util.TreeMap, as
this data structure:
* provides ascending order of keys, that is useful for an ordered representation of keys/numbers;
* offers methods to obtain values from keys (get), to add and modify
keys/values (put) and to remove a key and its associated value (remove).
One of the things that make me dubious is how to implement the filesystem to
memory (load list) and the memory to filesystem (save list) bridge..
Thanks for any suggestion,
Paolo

Answer 1

I tought the same thing, initially. But, suppose that
name/number list contains 10000 records, and that I
change just one of them.
Do I understand correctly if I say that when I change
a record of the list and want to save the change, I
must iterate over 10000 records to save just one
change?Yes, or just wait with the save till the application is about to exit. (You would probably use a database instead if this was a commercial application)
Kaj