Question

I am copying directories and files from one windows server to another windows server using Swing and that works fine. I want to have a Joption Messagedialog pop up when the windows server goes down unexpectedly while copying so gave it in the catch block but it never dispays the pop up when the server goes down(I restart the windows server manually while copying but cannot see the pop up). Can someone help and here is the code

try {
    textarea.append("Copying " + sourceFile.getAbsolutePath()
        + "   to " + targetFile.getAbsolutePath());
    is = new BufferedInputStream(new FileInputStream(sourceFile));
    bos = new BufferedOutputStream(new FileOutputStream(targetFile));

    long fileBytes = sourceFile.length();
    long soFar = 0;

    int theByte;

    while ((theByte = bis.read()) != -1) {
        bos.write(theByte);

        setProgress((int) (copiedBytes++ * 100 / totalBytes));
        publish((int) (soFar++ * 100 / fileBytes));
    }

    bis.close();
    bos.close();
    publish(100);
    textarea.append(" Done!\n");
} catch (Exception excep) {
    task.cancel(true);
    bos.flush();
    bis.close();
    bos.close();
    jf2 = new JFrame();
    jf2.setSize(401, 401);
    jf2.setDefaultCloseOperation(jf2.EXIT_ON_CLOSE);
    JOptionPane.showMessageDialog(jf2,
        "The Server is not accessible or it may be down because of Network Issue",
        "ERROR", JOptionPane.ERROR_MESSAGE);
} finally {
    if (bis != null) {
        bis.close();
    }
    if (bos != null) {
        bos.close();
    }
}

Answer 1

Your try-catch is a little akward.

You try and close the streams on the event of an exception AND within the finally block.

Finally is guaranteed to be called regardless, so you can save yourself some code by using it to close of the steams..

try {
    textarea.append("Copying " + sourceFile.getAbsolutePath()
                    + "   to " + targetFile.getAbsolutePath());
    is = new BufferedInputStream(new FileInputStream(sourceFile));
    bos = new BufferedOutputStream(new FileOutputStream(targetFile));

    long fileBytes = sourceFile.length();
    long soFar = 0;

    int theByte;

    while ((theByte = bis.read()) != -1) {
        bos.write(theByte);

        setProgress((int) (copiedBytes++ * 100 / totalBytes));
        publish((int) (soFar++ * 100 / fileBytes));
    }

    // Not required, finally will take care of it...
    //bis.close();
    //bos.close();
    publish(100);
    // !! THIS IS VERY, VERY NAUGHTY !!
    textarea.append(" Done!\n");
} catch (Exception excep) {

    JOptionPane.showMessageDialog(null, "The Server is not accessible or it may be down because of Network Issue", "ERROR", JOptionPane.ERROR_MESSAGE);
    task.cancel(true);

} finally {

    try {
        // techniqually, this gets taken care of when you close the stream,
        // but I tend not to trust it either...
        bos.flush();
    } catch (Exception e) {
    }

    try {
        bis.close();
    } catch (Exception e) {
    }
    try {
        bos.close();
    } catch (Exception e) {
    }

}

It appears that your code is using a SwingWorker, but you call textarea.append(" Done!\n") within it. This is VERY, VERY bad.

Your process method needs to be capable of doing this…Basically when you process receives 100, it should be capable of updating the text area.

You could also allow the exception to handled else where, allowing the doInBackground method to throw the exception. This would allow you to use the done method and the get method to determine if an exception has occurred, the added benefit of which is done is called within the EDT