jdbc connection problem

hi everybody,

i have a problem connecting to postgres using the jdbc driver.

took the org.postgresql.test.jdbc2.DriverTest and modified it to use

    String url = "jdbc:postgresql://localhost/testdb";
    String user = "username";
    String pass = "password";


i get the exception
org.postgresql.util.PSQLException: Connection Refused. Check that the hostname and port are correct and that the
postmasteris accepting TCP/IP connections. 

however, using
psql -h localhost -U username -W
and then specifying the password works. so i do not see how this could be a general problem with postgresql listening
onthe wrong interface or not accepting connections from the local host. 

btw, i use psql 8.1.4 on ubuntu, jdbc is postgresql-8.1-408.jdbc2.jar

any ideas?

thanks,
david