How to test if a file is “complete” (completely written) with Java

Question

Let\'s say you had an external process writing files to some directory, and you had a separate process periodically trying to read files from this directory. The problem to

Answer 1

I had no option of using temp markers etc as the files are being uploaded by clients over keypair SFTP. they can be very large in size.

Its quite hacky but I compare file size before and after sleeping a few seconds.

Its obviously not ideal to lock the thread but in our case it is merely running as a background system processes so seems to work fine

private boolean isCompletelyWritten(File file) throws InterruptedException{
    Long fileSizeBefore = file.length();
    Thread.sleep(3000);
    Long fileSizeAfter = file.length();

    System.out.println("comparing file size " + fileSizeBefore + " with " + fileSizeAfter);

    if (fileSizeBefore.equals(fileSizeAfter)) {
        return true;
    }
    return false;
}

Note: as mentioned below this might not work on windows. This was used in a Linux environment.