private static boolean isInteger(String s) {
    boolean isInt = s.length() > 0;
    for (int i = 0; i < s.length(); i++) {
      if (s.charAt(i) < '0' || s.charAt(i) > '9') {
        isInt = false;
        break;
      }
    }
    return isInt;
  }
Returns the value of the argument as an unsigned integer in seconds since '1970-01-01 00:00:00'
UTC.
amoro-format-mixed/amoro-mixed-flink/amoro-mixed-flink-common/src/main/java/org/apache/amoro/flink/util/DateTimeUtils.java