It's probably not the "Java code" itself that's going to change - it's going to (possibly) be stuff like changing database connection information, and SQL queries. Now as for how much change - I don't know... I'm not sure how much changed between SQL Server 2000 and 2005.
Write once, run anywhere, because there's nowhere to hide! - /. A.C.
subject: Code compatibilty in j2ee application while migrating from SQL Server 2000 to SQL Server 2005