static File oneOfTheFiles(S... paths) {
  if (paths != null) for (S path : paths)
    if (fileExists(path))
      ret newFile(path);
  null;
}

static File oneOfTheFiles(File... files) {
  ret oneOfTheFiles(asList(files));
}

static File oneOfTheFiles(Iterable<File> files) {
  if (files != null) for (File f : files)
    if (fileExists(f))
      ret f;
  null;
}