How to get the current user ID after sign on to AS400

Hi, all,

I have a program using JDBC driver to access DB2 on AS400.  I will let the
different users to use different testing databases(libraries) on AS400.  So
after the program connected to AS400, I need to know the user ID who just
signed on AS400 in order to set up a URL as
"jdbc:as400://mysystem/databaseXYZ".  Then use this URL to make a
connection, such as:  con = DriverManager.getConnection(URL);

Is there anyway I could get the current userID, something like:

if (userID.equals("John")){
        URL = "jdbc:as400://mysystem/databaseJohn";
}
else if (userID.equals("Tom")){
        URL = "jdbc:as400://mysystem/databaseTom";
}

con = DriverManager.getConnection(URL);

Thanks for any helps.

Wayne