Documentation for working with PG interval types via JDBC

Hi everyone,

PG has an interval data type. Via google searches and the mail
archive[1] I learned that PG jdbc driver has
org.postgresql.util.PGInterval type which however is not listed in the
public API[2].
Is there some documentation on the way it is supposed to be used, how it
is mapped to Java types (it is a PG extension after all), or is my best
shot the source code?

Kind regards:
al_shopov

[1]

http://groups.google.com/group/pgsql.interfaces.jdbc/browse_thread/thread/c3aab813c0c78c11/3a17a0ed5bff5b33?lnk=gst&q=interval#3a17a0ed5bff5b33
[2] http://jdbc.postgresql.org/documentation/publicapi/index.html