Alan,
Catching OverlappingFileLockException is usually a sign of a mis-use. Can you summarize how this comes about (given the locking on "locks").
Malicious intent or ignorant mis-use by code outside of the FileHandler can turn the FileHandler into a victim of that misuse. ======= public static void main(String[] args) throws Exception { Path p = Files.createTempFile("test", "test"); try (FileChannel pathogen = FileChannel.open(p, CREATE, WRITE)) { FileLock lck = pathogen.lock(); System.out.println(lck); try (FileChannel fileHandler = FileChannel.open(p, WRITE, APPEND)) { FileLock fhl = fileHandler.lock(); System.out.println(fhl); } } finally { Files.deleteIfExists(p); } } ========= sun.nio.ch.FileLockImpl[0:9223372036854775807 exclusive valid] Exception in thread "main" java.nio.channels.OverlappingFileLockException ================= Jason