Error get after upgrading postgresql server

Hi all, I get the following error after update postgresql server to 7.2
series when running jdbc project.

[cvs@desktop src]$ java initdb
Exception in thread "main" Something unusual has occured to cause the
driver to fail. Please report this exception: Exception:
java.sql.SQLException: FATAL 1:  No pg_hba.conf entry for host
127.0.0.1, user carfield, database smartcarpark

Stack Trace:

java.sql.SQLException: FATAL 1:  No pg_hba.conf entry for host
127.0.0.1, user carfield, database smartcarpark

        at org.postgresql.Connection.openConnection(Connection.java:178)
        at org.postgresql.Driver.connect(Driver.java:149)
        at java.sql.DriverManager.getConnection(DriverManager.java:543)
        at java.sql.DriverManager.getConnection(DriverManager.java:216)
        at initdb.main(initdb.java:11)
End of Stack Trace

        at org.postgresql.Driver.connect(Driver.java:166)
        at java.sql.DriverManager.getConnection(DriverManager.java:543)
        at java.sql.DriverManager.getConnection(DriverManager.java:216)
        at initdb.main(initdb.java:11)

Seem I need to modify a file call pg_hba.conf, and my system have a good
sample tell me how to edit. However, I don't know where should I put the
file. Can anyone tell me?