Is it any optimization for BATCH queries for Derby?

how about the speed for inserts?
which one will be suitable for batchquery?  the statement or preparestatement ?

it seems a little bit slow to insert a bunch of data into the DB. 
it is about 7ms for ORACLE (100 queries in batch)
but it tooks 20ms for DERBY (100 queries in batch)
and the worse case is that it goes slower and slower if I have more than 30000 rows data in it.
there is one index in the table. I don't think it gonna cost too much.

any idea to speed up?