[jdbc] how can I implement copy feature in pgsql with jdbc?

hi,
the psql has a copy command can copy a file to a table or copy a table to a
file.
is it possible to implement the same feature in jdbc?
what I want to do is export some data file to postgresql with java in an
easy way.
I'm new to postgresql and have not hack the code of psql.c
Thanks for any help.

BR
kevin