Using Collections and initialisation

Question

I am not in the IT business but I am trying to teach myself Java using the JBuilder IDE.
I am creating an application which will contain the personal details of each individual user along with a record of the training/work they undertake on different days. The user logs in and accesses their personal info using a password. At the moment I am constructing each persons details in a Vector in case I want to add more attributes later, although there may be better options. I am therefore creating a PersonDetail class which extends Vector and which has the following elements:
String name;
String initials;
String pinNumber;
char[] password;
Vector workRecord; (Vector, because it will expand all the time as new records about what work the user does are added.)
Therefore I could have many instances of this PersonDetail class floating about, and I assume I should store them in something that should not take duplicates such as a Set or HashSet. I can then iterate through them to check the details of a person logging in. If this sounds feasible, should this overall holding collection be static i.e. one class instance only? If so, where should this static instance be declared/created to stop it being initialised more than once? I have created some GUI�s using Swing, but without a decent underlying system for storing the information the GUIs collect, its never really going to work efficiently.
Any guidance on a better way of storing the information or an answer to my specific query warmly appreciated - and apologies if what I have said doesn't make sense!
Paul D

Answer 1

Your approach seems OK to me. The problem you will have is that the data is volatile, i.e. you will lose it when the program exits, unless you serialize to a file. Use the Serializable interface to acheive this. Once you get the hang of it, its very convenient. Check out Suns tutorials.
Alternatively, you could put your data into an SQL database (MS access SQLServer MySQL etc..) and use JDBC to access/update it. The trick here is setting up the JDBC/ODBC access, and it does require some basic understanding of SQL.
Hope this helps.