What is the fastest way to communicate with Java application?

What is the fastest way to communicate with Java application?

Consider a setting of a large database and an application which needs to
interact with the database. If you were building it from scratch, what
communication technology would you use, if the objective is to maximize
throughput? Important requirement is, however, that the application using
the database is not written in Java. There is however a relaxed
requirement: it needs not to run on anything other then Linux, and if only
a particular JVM provides this feature, but not the others, I'm ok with
that too.
In other words, I would imagine there must be some kind of foreign
function interface and a way to represent Java objects (at least the most
basic types) in memory and pass them to the Java database w/o ever needing
to print them, open sockets, write on pipes, because all of that would
imply tons of memory de/allocation, de/serialization and so on. But since
I'm not really a Java person, I don't know what I'm looking for.