JNI call to find stability of file

Question

We receive files from third-party servers and these files are written to the disk in a windows machine. I am trying to find out how I can find out if the file is completely written to disk. I don't know the size of the file. Once the file is written completely i would like to process them. There is no other indication that the file transfer is complete.
Is there a low-level call I can make from a Java program to do this ?

Answer 1

As stated - impossible. Not in java nor any other way to do it on a computer either.
As an example say I, a human, write my hours to a file when I leave work. Today it is at 8pm. Tomorrow it is at 6pm. Friday it is at 3 pm. But if I forget on Friday then I might enter the time on Monday at 10am.
How is the computer supposed to know, without any other information when the file is "complete"? Is it done every day at midnight? That won't work if I forget.
So you need to first understand the exact process is that "receives" the file. For example
1. The files always arrive in directory X with todays date.
2. The files are received via FTP and are continously written (meaning that it isn't appended to but not that pauses do not occur.)
For the above you would then do the following.
1. A 2 am you can then look for files in X with yesterdays date.
2. You look at the size and verify that after 5 minutes (or 10) that the file size has not changed.
3. You then copy the file to a different location.
4. You then process that file.
5. If the file is not there are all then you issue an error message.