autocommit (true/false) for more than 1 million records

Hello,

Trying to insert into one table with 1 million records through java JDBC
into psql8.3. May I know (1) or (2) is better please?

(1) set autocommit(true)
(2) set autocommit(false)
      commit every n records (e.g., 100, 500, 1000, etc)

Thanks a lot!
Emi