static void validateFiles(List<String> newFiles) throws IllegalArgumentException {
    SessionState ss = SessionState.get();
    Configuration conf = (ss == null) ? new Configuration() : ss.getConf();

    for (String newFile : newFiles) {
      try {
        if (Utilities.realFile(newFile, conf) == null) {
          String message = newFile + " does not exist";
          throw new IllegalArgumentException(message);
        }
      } catch (IOException e) {
        String message = "Unable to validate " + newFile;
        throw new IllegalArgumentException(message, e);
      }
    }
  }
@return username from current SessionState authenticator. username will be
        null if there is no current SessionState object or authenticator is
        null.
ql/src/java/org/apache/hadoop/hive/ql/session/SessionState.java