您可以尝试以下变体之一：

// add this function: it converts intervalDS to Time/Timestamp
    public static Time intervalDStoTime(INTERVALDS intervalds) throws ParseException {
        SimpleDateFormat intervalFormat = new SimpleDateFormat("dd hh:mm:ss.SSS");
        java.util.Date parsedDate = intervalFormat.parse(intervalds.stringValue());
        Time time = new java.sql.Time(parsedDate.getTime());
        // or you can replace previous line with this one if yu will need timestamp:
        // Timestamp timestamp = new java.sql.Timestamp(parsedDate.getTime());
        return time;
    }

//...
// your code:
    //Original:
    oracle.sql.INTERVALDS startTime = rs.getINTERVALDS("START_TIME");
    System.out.println("Original:" + startTime);
    // 1: interval to time:
    Time time = intervalDStoTime(startTime);
    System.out.println("ToTime: " + time);
    // 2: + format
    System.out.println("ToTime + format: " + new SimpleDateFormat("hh:mm").format(time));
    // 3: format bytes
    byte[] bytes = startTime.toBytes();
    int hour = bytes[4] - 60;
    int minute = bytes[5] - 60;
    String hhmm = String.format("%02d:%02d", hour, minute);
    System.out.println("toBytes + format: " + hhmm);