Unix domain instead of TCP socket connections with JDBC.

Using the org.postgresql.Driver JDBC driver is it possible to connect
to Postgres using a unix domain socket instead of a TCP socket (so you
don't have to start the postmaster with -i)? Using a TCP socket
instead of a unix socket seems to slow down requests that return large
result sets by a factor of 3 on the same machine. What's the point of
all the extra CPU overhead if you're on the same machine? A
high-volume server can really do without the extra overhead. Also, for
security reasons it would be slightly nicer to run Postgres without -i
just so there's one less port popping up when you port-scan.