null pointer exception

dear mailing list

i am trying to built a jdbc connection to postgres .... but

db = DriverManager.getConnection("jdbc:postgresql://url", "username",
"");

throws a null pointer exception. could anyone tell me what might be the
reason? many many thanks in advance.


-- 
All the best
Chris

***********************************************************        
    Mr. C. Setzkorn (Phd Student)                   Department of Computer Science                University of
Liverpool               Chadwick Building, room G47          Peach Street, Liverpool L69 7ZF           United Kingdom
                                           Email:    chris@csc.liv.ac.uk                Phone:    0044 151 794 3692
                     Fax:        0044 151 794 3715 homepage:    http://www.csc.liv.ac.uk/~chris