Writing a file listener

[matzahboy]

I have a file that a program written in another language is going to change every few minutes. I want my java program to run a set of code (which I've already written) every time this file changes. How would I do this?

The source path for the file is "C:\\outputFile.txt".

[Fubarable]

I've never done a file listener, so sorry but I can't help you, but I can wish you a happy Matzah week.

[matzahboy]

Do you think I should post this in the "advanced" section?

[Fubarable]

I'm not sure. If you do decide to do this though, post links from one post to the other.

[toadaly]

You have to poll every so often to see if lastModified has changed. There is no event service from the file system in java.

[matzahboy]

If I wanted to poll it every 20 seconds, how would I do that?

[DarrylBurke]

With a Timer.

db

[matzahboy]

I've done google searches on this. I've looked at websites/tutorials. I know that I need to use a timer and a filelistener. But how do I write the code? I understand what I need to use by not how to use it.

[einarb]

I've done google searches on this. I've looked at websites/tutorials. I know that I need to use a timer and a filelistener. But how do I write the code? I understand what I need to use by not how to use it.

I've never heard of a filelistener interface.. My guess would be to use a Timer and a TimerTask, in some way like this

Start the timer something like this

import java.util.Timer;

public class SomeClass {
	private static final long TIME_TO_START = ...;
	private static final long DELAY_BETWEEN_POLLS = ...;
	Timer timer = new Timer();
	// ...

	public void startFilePoller(File file) {
		timer.scheduleAtFixedRate(new FileListener(file), TIME_TO_START, DELAY_BETWEEN_POLLS);
	}
	//...

And you need an implementation of TimerTask, which will work somewhat similar to a listener

public class FileListener extends TimerTask {
	// ...
	public FileListener(File file, ..) {
		this.file = file;
		//..
	}

	@Override
	public void run() {
		if (isFileModified()) {
			// do whatever needs doing if file has been modified
		}
	}

	private boolean isFileModified(){
		//...

Hope this can get you started