No results were returned by the query.

I have some postgresql calls in a jsp file. I can do select calls with no
problem. When i do an update call I get

javax.servlet.ServletException: No results were returned by the query

the code snipit is:
PreparedStatement ps = conn.prepareStatement(
"update users set firstname = ? where userid = ?");
ps.setString(1, firstname);
ps.setString(2, userid);
ps.executeQuery();

I dont except any 'results' from an update statment, so im really confused
by the exception. The statement does get executed - i can see the change
in the database. Im just trying to avoid the exception.

Don