public static String addPrefix2FilePath(String prefix, String file) {
    if (!new File(file).isAbsolute() && prefix != null && prefix.length() > 0) {
      if (!prefix.endsWith(File.separator)) {
        file = prefix + File.separatorChar + file;
      } else {
        file = prefix + file;
      }
    }
    return file;
  }
Add a prefix to a relative path file
iotdb-core/node-commons/src/main/java/org/apache/iotdb/commons/utils/FileUtils.java