Best method to trigger events in a constantly-running program?

I need to have a particular Java application always running in the background on my Linux machine (like a daemon) (it's a singleton -- no two instances will run simultaneously). However, I need to be able to send "events" to this application from another program, where an event is as simple as a line of text that the application interprets as some action. These events will be invoked by a non-Java program, so it should be possible for them to be called by, for example, a shell script that is executed. What's the best way to do this? The only idea I could come up with is:
The program writes the event to a file. The main Java application watches a particular file for changes -- when it encounters changes, it reads the file and takes the appropriate action.
Anything more elegant than that?
EDIT: Would it be better to have my main application listen on a particular port, and have the invoking application send the event information across that port?
Edited by: Tony_R on Dec 6, 2009 10:12 PM

Tony_R wrote:
The program writes the event to a file. The main Java application watches a particular file for changes -- when it encounters changes, it reads the file and takes the appropriate action.
Anything more elegant than that?See below.
EDIT: Would it be better to have my main application listen on a particular port, and have the invoking application send the event information across that port?Yes, a local socket is usually the best solution. On Unix, it might be possible to use a (named) pipe, but sockets should work just fine and are the standard solution for this sort of thing.

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