Try to be precise here: commit() and setAutoCommit() are Connection object methods and have little to do with Access. Look at the javadoc for this class.

In SQL, you must commit your changes explicitly. With JDBC, you can use autoCommit mode (a Connection object mode): then a commit is silently sent to the database after every update call.

If you don't see any change in your Access file, maybe it's just because no commit is done in your program. You can add one of the two:
conn.setAutocommit(true); // at the beginning
conn.commit(); // before quitting, when all's done.

Laurent