@NotNull
  static File createNewDir(File parent, String prefix, int max) {
    synchronized (ourDirectoryLock) {
      for (int i = 0; i < max; i++) {
        String name = prefix + i;
        File f = new File(parent, name);
        if (!f.exists()) {
          boolean createSuccessFull = f.mkdirs();
          if (createSuccessFull) {
            return f;
          }
        }
      }
      throw new RuntimeException("No available dir found");
    }
  }
@NotNull
  static File createNewDir(File parent, String prefix, int max)