How to detect filesystem has changed in java

Question

Hi all,

I would like to know how to efficiently implement filesystem changes in java? Say I got a file in a folder and modify that file. I would like to be notified by java about this change as soon as possible(no frequently polling if possible.).

Because I think I could call java.io.file.lastModified every few seconds but I don't like the sound of that solution at all.

alfred@alfred-laptop:~/testje$ java -version
java version "1.6.0_18"
Java(TM) SE Runtime Environment (build 1.6.0_18-b07)
Java HotSpot(TM) Server VM (build 16.0-b13, mixed mode)

Many thanks, Alfred

Answer 1

I doubt that there is a pure java way to do this. Operating systems offer APIs to monitor file system a activity. You will probably need to call those APIs.

Answer 2

Take a look at JNotify, which performs this type of monitoring.

Java 7 will have some more advanced APIs (WatchService) for this sort of work which will eliminate polling on the OSes that support this.