If you plan to use this code on a single platform, you may be able to use NIO's FileLock facility. But read the documentation carefully, and note that on many platforms, the lock is only advisory.
Another approach is to have one process write the file with a name that your process won't recognize, then rename the file to a recognizable name when the write is complete. On most platforms, the rename operation is atomic if the source and destination are the same file system volume.
