How to tell when a File is "Done" copying into a watched Directory?

I'm using the WatchService API to watch a directory, and getting ENTRY_CREATE events when a user starts copying a file into the directory. The files I'm working with can be large, though, and I'd like to know when the copy is finished. Is there any built in java API I can use to accomplish this, or am I best off to just keep track of the created files' size and start processing when the size stops growing? EDIT: Here is my example code: ``` package com.example; import java.io.File; import java.nio.file.FileSystems; import java.nio.file.Path; import java.nio.file.StandardWatchEventKinds; import java.nio.file.WatchEvent; import java.nio.file.WatchKey; import java.nio.file.WatchService; public class Monitor { public static void main(String[] args) { try { String path = args[0]; System.out.println(String.format( "Monitoring %s", path )); WatchService watcher = FileSystems.getDefault().newWatchService(); Path watchPath = FileSystems.getDefault().getPath(path); watchPath.register(watcher, StandardWatchEventKinds.ENTRY_CREATE, StandardWatchEventKinds.ENTRY_MODIFY); while (true) { WatchKey key = watcher.take(); for (WatchEvent<?> event: key.pollEvents()) { Object context = event.context(); System.out.println( String.format( "Event %s, type %s", context, event.kind() )); } } } catch (Exception e) { // TODO Auto-generated catch block e.printStackTrace(); } } } ``` Which Produces this output: ``` Monitoring /Users/ericcobb/Develop/watch Event .DS_Store, type ENTRY_MODIFY Event 7795dab5-71b1-4b78-952f-7e15a2f39801-84f3e5daeca9435aa886fbebf7f8bd61_4.mp4, type ENTRY_CREATE ```