unique id's and incr

During the creation of my database, I'm doing a:

CREATE UNIQUE INDEX account_idx ON Accounts (account_id);

to add new rows to my table and keep the id's unique.

During runtime (accessing by JDBC), is there anyway when adding a new row to a table to know the last id entry so as to incr the next one for a new id. I was thinking there might be a way to do this w/o having to query the table for the last id and incr the id before I do another insert.

Any help much appreciated.