FileListener not catching file change

Question

I did a few searches to try and find a File listener that would listen for changes made to a file such as contents or extensions changes. I cam upon the following interface and class:
package customdisc;
import java.io.File;
public interface FileListener
    void fileChanged(File file);
package customdisc;
import java.util.*;
import java.io.File;
import java.lang.ref.WeakReference;
* Class for monitoring changes in disk files.
* Usage:
* 1. Implement the FileListener interface.
* 2. Create a FileMonitor instance.
* 3. Add the file(s)/directory(ies) to listen for.
* fileChanged() will be called when a monitored file is created,
* deleted or its modified time changes.
public class FileMonitor
    private Timer timer_;
    private HashMap files_; // File -> Long
    private Collection listeners_; // of WeakReference(FileListener)
    public FileMonitor(long pollingInterval)
        files_ = new HashMap();
        listeners_ = new ArrayList();
        timer_ = new Timer(true);
        timer_.schedule(new FileMonitorNotifier(), 0, pollingInterval);
    public void stop()
        timer_.cancel();
    public void addFile(File file)
        if (!files_.containsKey(file))
            long modifiedTime = file.exists() ? file.lastModified() : -1;
            files_.put(file, new Long(modifiedTime));
    public void removeFile(File file)
        files_.remove(file);
    public void addListener(FileListener fileListener)
// Don't add if its already there
        for (Iterator i = listeners_.iterator(); i.hasNext();)
            WeakReference reference = (WeakReference) i.next();
            FileListener listener = (FileListener) reference.get();
            if (listener == fileListener)
                return;
// Use WeakReference to avoid memory leak if this becomes the
// sole reference to the object.
        listeners_.add(new WeakReference(fileListener));
    public void removeListener(FileListener fileListener)
        for (Iterator i = listeners_.iterator(); i.hasNext();)
            WeakReference reference = (WeakReference) i.next();
            FileListener listener = (FileListener) reference.get();
            if (listener == fileListener)
                i.remove();
                break;
    private class FileMonitorNotifier extends TimerTask
        public void run()
// Loop over the registered files and see which have changed.
// Use a copy of the list in case listener wants to alter the
// list within its fileChanged method.
            Collection files = new ArrayList(files_.keySet());
            System.out.println("There are " + files.size() + " files");
            for (Iterator i = files.iterator(); i.hasNext();)
                File file = (File) i.next();
                long lastModifiedTime = ((Long) files_.get(file)).longValue();
                long newModifiedTime = file.exists() ? file.lastModified() : -1;
// Chek if file has changed
                if (newModifiedTime != lastModifiedTime)
// Register new modified time
                    files_.put(file, new Long(newModifiedTime));
// Notify listeners
                    for (Iterator j = listeners_.iterator(); j.hasNext();)
                        WeakReference reference = (WeakReference) j.next();
                        FileListener listener = (FileListener) reference.get();
// Remove from list if the back-end object has been GC'd
                        if (listener == null)
                            j.remove();
                        else
                            listener.fileChanged(file);
}Now, in my listening class I have instantiated FileMonitor and I am implementing FileListener.
Here are the few parts of my listening class:
public class CreateDisc implements FileListener
    private static File isoImage;
    private static File discLabel;
    private static DVDOrder dvdOrder;
    private static Order order;
    private static File job;
    private static FileMonitor fileMonitor = new FileMonitor (1000);
    public CreateDisc(File iso, File img, Order order)
        try
            fileMonitor.addListener (this);
            CreateDisc.isoImage = iso;
private static void buildJob()
        Writer output = null;
        try
            String isoPath = CreateDisc.isoImage.getAbsolutePath();
            String labelPath = CreateDisc.discLabel.getAbsolutePath();
            int priority = CreateDisc.order.getDiscPriority();
            String jobPath = Config.BURNER_JOB_PATH + CreateDisc.order.getCustName() + "_" + CreateDisc.order.getWebID() + ".meow";
            job = new File(jobPath);
            System.out.println("Adding \"job\" to the monitor...");
            fileMonitor.addFile(job);
            output = new BufferedWriter(new FileWriter(job));
            // Create a JobID
            output.write("JobID=" + CreateDisc.order.getCustName() + "_" + CreateDisc.order.getWebID() + "\n");
            // Create a ClientID
            output.write("ClientID=" + CreateDisc.order.getCustName() + "_" + CreateDisc.order.getWebID() + "\n");
            // Set a priority if we need one; otherwise, the application defaults to 4
            if (priority < 4)
                output.write("Importance=" + priority + "\n");
            // Set the ISO path
            output.write("ImageFile=" + isoPath + "\n");
            // Set the data type if it's a DVD
            if (CreateDisc.order.getDiscType().equals("DVD"))
                output.write("DataImageType=UDF\n");
            // Close the disc
            output.write("CloseDisc=YES\n");
            // The disc label path
            output.write("PrintLabel=" + labelPath + "\n");
            // Give the disc a name
            output.write("VolumeName=" + CreateDisc.order.getDiscName() + "\n");
            // Reject the disc if it isn't blank
            output.write("RejectIfNotBlank=YES\n");
            // Notify the client on errors
            output.write("NotifyClient=YES");
            // Set the drive ID
            //output.write("DriveID=");
            // Set the bin to pull the discs from
            //output.write("BinID=");
        catch (IOException ex)
            Logger.getLogger(CreateDisc.class.getName()).log(Level.SEVERE, null, ex);
        } finally
            try
                output.close();
            catch (IOException ex)
                Logger.getLogger(CreateDisc.class.getName()).log(Level.SEVERE, null, ex);
    public void fileChanged(File file)
        System.out.println("File " + file.getName() + " has changed.");
    }So, I instantiate the FileMonitor, add my CreateDisc class as the listening object, and then I add a File object to the listener. I know the file is getting added because my output is as follows:
There are 0 files
There are 0 files
There are 0 files
params =  -quiet -o C:\ISO\224561\224561.iso -dvd-video C:\DOCUME~1\tlee\LOCALS~1\Temp\KaraokeDVDBurner\dvd
There are 0 files
Adding "job" to the monitor...
There are 1 files
There are 1 filesWhenever I modify the file at all, whether it be the file contents or removing the file completely, my abstract method fileChanged() is never called. So after knowing that my file is added to the FileMonitor object, I'm lost as to why it isn't noticing changes. Any thoughts?

Answer 1

Well I figured it out. Turns out I was referencing the class instead of instantiating it. fileMonitor.addListener (this); was in the constructor, but the constructor was never called.
So, this works.
// Check to see if we are currently making an ISO
                if(!Config.IS_MAKING_ISO && !newOrderModel.isEmpty())
                    Config.IS_MAKING_ISO = true;
                    new Thread()
                        @Override
                        public void run()
                            // CreateDisc.makeDisc((Order) CustomUI.newOrderModel.get(0)); class reference
                            CreateDisc createDisc = new CreateDisc();
                            createDisc.makeDisc((Order) CustomUI.newOrderModel.get(0));
                    }.start();
                }Now onto the WeakReference. I don't finalize the CreateDisc object, but once all file activity has completed and the File references are gone, the system will finalize it, correct? And then it will be GCed.