code: private RegularFile getOrCreateRegularFileWithWriteLock(
        JimfsPath path, Set<OpenOption> options, FileAttribute<?>[] attrs) throws IOException {
      store.writeLock().lock();
      try {
        File file = createFile(path, store.regularFileCreator(), options.contains(CREATE_NEW), attrs);
        // the file already existed but was not a regular file
        if (!file.isRegularFile()) {
          throw new FileSystemException(path.toString(), null, "not a regular file");
        }
        return open((RegularFile) file, options);
      } finally {
        store.writeLock().unlock();
      }
    }
docs: Gets or creates a new regular file with a write lock (assuming the file does not exist).