1) Use Apache Commons I/O. It has a file monitor class.
2) Wait until
Java 7 comes out. It too has a file monitor class.
3) Write your own scheduled job, using a Timer, ScheduledExecutor, Quartz or something similar.
Of course, 1 would be the easiest for a short term solution. In the Java in General forum there was a
thread about this too, and after quite some work I managed to figure out (and post) how to use it for java.io.File.