java String时间转为时间戳

String startDate="2017-08-15";
        String endDate="2017-08-15";
        
        SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");
        int startDay = 0;
        int endDay = 0;
        try {
            Date dateStart = format.parse(startDate);
            Date datEnd = format.parse(endDate);

            startDay = (int) (dateStart.getTime() / 1000);
            endDay = (int) (datEnd.getTime() / 1000);
        } catch (Exception e) {
            e.printStackTrace();
        }
        System.err.println(startDay);
        System.err.println(endDay);