code: public static String getUserHomeDir(String base) {
          String userhome = System.getProperty("user.home");
          File file = new File(userhome, base);
          if (file.exists()) {
              if (!file.isDirectory()) {
                  // LOGGER.error("{} exists, but not directory", file.getAbsolutePath());
                  throw new SofaRpcRuntimeException(file.getAbsolutePath() + " exists, but not directory");
              }
          } else {
              file.mkdirs(); // 可能创建不成功
          }
          return file.getAbsolutePath();
      }
docs: 得到USER_HOME目录
  
  @param base 用户目录下文件夹
  @return 得到用户目录