public static String formatTimestampString(String dateStr, String toFormat, TimeZone tz) {
    // use yyyy-MM-dd HH:mm:ss as default
    return formatTimestampString(dateStr, TIMESTAMP_FORMAT_STRING, toFormat, tz);
  }
Parses a fraction, multiplying the first character by {@code multiplier}, the second character
by {@code multiplier / 10}, the third character by {@code multiplier / 100}, and so forth.

<p>For example, {@code parseFraction("1234", 100)} yields {@code 123}.
amoro-format-mixed/amoro-mixed-flink/amoro-mixed-flink-common/src/main/java/org/apache/amoro/flink/util/DateTimeUtils.java