File.createNewFile () creates files with the last modified time before the actual creation time

I am using JPoller to detect changes to files in a specific directory, but it is missing files because they end up timestamped earlier than their actual creation time. This is how I test:

public static void main(String [] files)
{
    for (String file : files)
    {
        File f = new File(file);
        if (f.exists())
        {
            System.err.println(file + " exists");
            continue;
        }

        try
        {
            // find out the current time, I would hope to assume that the last-modified
            // time on the file will definitely be later than this
            System.out.println("-----------------------------------------");
            long time = System.currentTimeMillis();

            // create the file
            System.out.println("Creating " + file + " at " + time);
            f.createNewFile();

            // let see what the timestamp actually is (I've only seen it <time)
            System.out.println(file + " was last modified at: " + f.lastModified());

            // well, ok, what if I explicitly set it to time?
            f.setLastModified(time);
            System.out.println("Updated modified time on " + file + " to " + time + " with actual " + f.lastModified());
        }
        catch (IOException e)
        {
            System.err.println("Unable to create file");
        }
    }
}

      

        
        
        
      

    

And this is what I get for the output:

-----------------------------------------
Creating test.7 at 1272324597956
test.7 was last modified at: 1272324597000
Updated modified time on test.7 to 1272324597956 with actual 1272324597000
-----------------------------------------
Creating test.8 at 1272324597957
test.8 was last modified at: 1272324597000
Updated modified time on test.8 to 1272324597957 with actual 1272324597000
-----------------------------------------
Creating test.9 at 1272324597957
test.9 was last modified at: 1272324597000
Updated modified time on test.9 to 1272324597957 with actual 1272324597000

      

        
        
        
      

    

This results in a race condition:

• JPoller records last check time as xyz ... 123
• File created in xyz ... 456
• The file with the last modified timestamp actually reads xyz ... 000
• JPoller looks for new / updated files with timestamp greater than xyz ... 123
• JPoller ignores the newly added file because xyz ... 000 is less than xyz ... 123
• I am pulling my hair out for a while.

I tried digging around in the code, but lastModified()

also createNewFile()

native calls end up being allowed, so I am left with little information.

For test.9

, I am wasting 957 milliseconds . What accuracy can I expect? Can my results vary depending on the operating system or file system? Suggested workarounds?

NOTE. I am currently running Linux with an XFS file system. I wrote a short program in C

, and the stat system call shows st_mtime

how truncate(xyz...000/1000)

.

UPDATE . I ran the same program as on Windows 7 with NTFS, andmaintains full millisecond precision. MSDN link @mdma provided additional notes that FAT filesystems are accurate to create at 10ms resolution, but only accessed with 2 seconds precision. So it really depends on the OS.