just to clarify your question, you're not populating the table via trigger then right? that's typically the favored approach but either work actually.
anyways, there's a before insert way and an after insert way of getting the id, i'll describe them both.
- after insert: select max(id-column) from your-table; this assumes that your sequence grows, not shrinks. (if it shrinks use min) and parse the result set.
- before insert, get the id from the sequence via select sequence_name.nextval from dual; and insert that value. i don't usually recommend this method unless it's for a smaller system.
other than that, I don't think there's anything special in the JDBC that is for handling sequence generation. there might be something native to oracle though, i'd check on OTN.