code: private FileStatus[] concurrentGlobInternal(Path fixedPath, PathFilter filter)
        throws IOException {
      ExecutorService executorService = Executors.newFixedThreadPool(2, DAEMON_THREAD_FACTORY);
      Callable<FileStatus[]> flatGlobTask = () -> flatGlobInternal(fixedPath, filter);
      Callable<FileStatus[]> nonFlatGlobTask = () -> super.globStatus(fixedPath, filter);
  
      try {
        return executorService.invokeAny(Arrays.asList(flatGlobTask, nonFlatGlobTask));
      } catch (InterruptedException | ExecutionException e) {
        throw (e.getCause() instanceof IOException) ? (IOException) e.getCause() : new IOException(e);
      } finally {
        executorService.shutdownNow();
      }
    }
docs: Use 2 glob algorithms that return the same result but one of them could be significantly faster
  than another one depending on directory layout.