The running class probably needs to be a server of some kind, with server loosely defined as any process that waits for requests from clients.
It's pretty easy to write a socket server that accepts simple
string requests from clients and sends string responses. See the
Sun Networking Tutorial for details - the Socket chapter builds simple clients and servers you can largely borrow.
Other forms of "being a server" get more complex but might be appropriate if you need to have more complex conversations between objects. RMI might be the next step up the ladder.
Does that seem to fit the problem?