Java日期推迟计算、日期大小

 /**
     * 日期推迟计算
     * @param date
     * @param num
     * @return java.util.HashMap<java.lang.String,java.lang.String>
     */
    public static String dateAdd(String date, int num) throws ParseException {
        SimpleDateFormat sj = new SimpleDateFormat("yyyy-MM-dd");
        Date dateFormat = sj.parse(date);
        Calendar calendar = Calendar.getInstance();
        calendar.setTime(dateFormat);
        calendar.add(calendar.DATE, num);
        //System.out.println("期望日期：" + sj.format(calendar.getTime()));
        return sj.format(calendar.getTime());
    }

 /**
     * 是否超过指定日期
     *
     * @param
     * @return
     */
    public boolean dateJudge(String start, String end) throws ParseException {
        SimpleDateFormat sj = new SimpleDateFormat("yyyy-MM-dd");
        Date startDate = sj.parse(start);
        Date endDate = sj.parse(end);
        if (startDate.before(endDate)) {
            return false;
        } else {
            return true;
        }
    }

 public static void main(String[] args) throws ParseException {
        String startDate = "2015-01-01";
        String endDate = "2015-01-15";
        String newDate = dateAdd(startDate, 1);

        while (dateJudge(newDate, endDate)) {
            String tempStartDate = dateAdd(newDate, -1);
            System.out.println(tempStartDate + "___" + newDate);
            newDate = dateAdd(newDate, 1);

        }

    }

public static void main(String[] args) throws ParseException {
        String startDate = "2015-01-01";
        String endDate = "2015-01-17";
        String newDate = startDate;

        while (dateJudge(newDate, endDate)) {
            if (dateJudge(dateAdd(newDate, 2), endDate)) {
                System.out.println(newDate.concat(" 00:00:00__________") + dateAdd(newDate, 2).concat(" 23:59:59"));
                newDate = dateAdd(newDate, 3);
            } else {
                break;

            }
        }
        while (dateJudge(newDate, endDate)) {
            System.out.println(newDate);
            newDate = dateAdd(newDate, 1);
        }
    }