problems with datestyle

Hi,

I'm using a java program to connect to a postgresql database (I'm using
postgresql version 7.2.1).
I'd like to retrieve a value of type DATE with ResultSet.getString()
method
in the format dd/mm/yyyy without make any more changes in the program.

I've already tried to Change PGDATESTYLE to "sql, european".
When I access database on the console whith postgres user all dates are
showed in format dd/mm/yyyy, but it doesn't with a java program.

How can I use postmaster whith options -o -e?

OR

How can I change datastyle in postgresql.conf?

Thanks in advance!