Questions about Listen/Notify mechanism

Hallo,

I need to write a Java app which deals with as low as possible network
resources. That's why the database should inform my Java app about
changes and I does not have to poll the database every 5 seconds to
recognize them.
I read the Postgresql-JDBC documentation about the Listen/Notify
commands. I do not understand that note

"A key limitation of the JDBC driver is that it cannot receive
asynchronous notifications and must poll the backend to check if any
notifications were issued."

Does that mean that the driver will poll the database, e.g. every 5
seconds? If so, that would not be acceptable for me, because that is
exactly what I want to avoid. The only advantage of using Listen/Notify
in that case would be that I don't need an extra notification table that
my trigger would fill. Am I wrong? Oo

I hope somebody can help me with that.

Regard,

Max