There are many directions to head after mastering the core Java language (assuming you've truly mastered the fundamentals of objects vs. merely learning the language syntax; if you haven't, then I'd recommend some remedial OO studies for starters). For example:
1. You could learn more about Java 2 Enterprise Edition technologies, used to build enterprise-level applications (often web-hosted);
2. You could learn more about the
JDBC API and connecting to ODBC databases;
3. You could master using XML with Java.
Take time to explore where the biggest demand is professionally, then go for it!
Best wishes,
Jacquie