code: public void setTime(
              final int hour,
              final int minuteOfHour,
              final int secondOfMinute,
              final int millisOfSecond) {
          long instant = getChronology().getDateTimeMillis(
              getMillis(), hour, minuteOfHour, secondOfMinute, millisOfSecond);
          setMillis(instant);
      }
docs: Set the time from fields.
  The date part of this object will be unaffected.
  
  @param hour  the hour
  @param minuteOfHour  the minute of the hour
  @param secondOfMinute  the second of the minute
  @param millisOfSecond  the millisecond of the second
  @throws IllegalArgumentException if the value is invalid