copy schema across different physical databases in db2
JDBC is not really going to answer your problem directly. It is a generic programming API for working with any database. So it can't possibly know about utilities that are specific to an implementation, be it DB2, Oracle, MySQL, etc.

I would look at using one of the utilities you mentioned above. That is their purpose. They assist with moving databases and/or data across environments. (There is also the restore redirect option as well, which is good if you are doing a backup/restore option).

If you insist on doing this through application code, then you will have to pass DDL through the JDBC API's (which dependent on your driver and your permissions, may or may not work). Or you would have to try to execute the DB2 utilities from "command line" through you program (look at the Runtime class to do this).

Again, I would keep this out of the application (perhaps you can share more of why you want to do this? That would help with answering your question). If you insist on doing it inside your application, you may also want to check out Stack Overflow, as you may get answers from a "programmatic" perspective.