日期时间处理

最近搞一个关于事件趋势的工程，然后对于日期的处理整理如下：


public class ZtDateUtil {

    private static final SimpleDateFormat formate = new SimpleDateFormat("yyyy-MM-dd");

    public static String getCurrentTime(Date date, int day) {
        Calendar cal = Calendar.getInstance();// 使用默认时区和语言环境获得一个日历
        cal.setTime(date);
        SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");// 通过格式化输出日期
        cal.add(Calendar.DAY_OF_MONTH, day);// 取当前日期
        return format.format(cal.getTime());
    }

    /*时间String转Date*/
    public static Date converToDate(String dateStr) {
        if (!StringUtils.isBlank(dateStr)){
            try {
                return formate.parse(dateStr);
            } catch (ParseException e) {
                e.printStackTrace();
            }
        }
        return null;
    }

    /**
     * 获得指定日期的前一天
     * @param specifiedDay
     * @return
     * @throws Exception
     */
    public static String getSpecifiedDayBefore(String specifiedDay, Integer i) {
        //SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd");
        Calendar c = Calendar.getInstance();
        Date date = null;
        try {
            date = new SimpleDateFormat("yy-MM-dd").parse(specifiedDay);
        } catch (ParseException e) {
            e.printStackTrace();
        }
        c.setTime(date);
        int day = c.get(Calendar.DATE);
        c.set(Calendar.DATE, day - i);

        String dayBefore = new SimpleDateFormat("yyyy-MM-dd").format(c.getTime());
        return dayBefore;
    }

    /**
     * 获得指定日期的后一天
     * @param specifiedDay
     * @return
     */
    public static String getSpecifiedDayAfter(String specifiedDay, Integer i) {
        Calendar c = Calendar.getInstance();
        Date date = null;
        try {
            date = new SimpleDateFormat("yy-MM-dd").parse(specifiedDay);
        } catch (ParseException e) {
            e.printStackTrace();
        }
        c.setTime(date);
        int day = c.get(Calendar.DATE);
        c.set(Calendar.DATE, day + i);

        String dayAfter = new SimpleDateFormat("yyyy-MM-dd").format(c.getTime());
        return dayAfter;
    }

    public static String getOpenDateCount(String openedDateInput, Integer i) {
        String openedDate = null;
        switch (i) {
            case 1:
                openedDate = ZtDateUtil.getSpecifiedDayBefore(openedDateInput, 1);
                break;
            case 2:
                openedDate = ZtDateUtil.getSpecifiedDayBefore(openedDateInput, 2);
                break;
            case 3:
                openedDate = ZtDateUtil.getSpecifiedDayBefore(openedDateInput, 3);
                break;
            case 4:
                openedDate = ZtDateUtil.getSpecifiedDayBefore(openedDateInput, 4);
                break;
            case 5:
                openedDate = ZtDateUtil.getSpecifiedDayBefore(openedDateInput, 5);
                break;
            case 6:
                openedDate = ZtDateUtil.getSpecifiedDayBefore(openedDateInput, 6);
                break;
            case 7:
                openedDate = ZtDateUtil.getSpecifiedDayBefore(openedDateInput, 7);
                break;
        }
        return openedDate;
    }

    /**
     * 获取两个日期相差几个月
     * @author 石冬冬-Heil Hilter(dd.shi02@zuche.com)
     * @date 2016-11-30 下午7:57:32
     * @param start
     * @param end
     * @return
     */
    public static int getMonth(Date start, Date end) {
        if (start.after(end)) {
            Date t = start;
            start = end;
            end = t;
        }
        Calendar startCalendar = Calendar.getInstance();
        startCalendar.setTime(start);
        Calendar endCalendar = Calendar.getInstance();
        endCalendar.setTime(end);
        Calendar temp = Calendar.getInstance();
        temp.setTime(end);
        temp.add(Calendar.DATE, 1);

        int year = endCalendar.get(Calendar.YEAR) - startCalendar.get(Calendar.YEAR);
        int month = endCalendar.get(Calendar.MONTH) - startCalendar.get(Calendar.MONTH);

        if ((startCalendar.get(Calendar.DATE) == 1) && (temp.get(Calendar.DATE) == 1)) {
            return year * 12 + month + 1;
        } else if ((startCalendar.get(Calendar.DATE) != 1) && (temp.get(Calendar.DATE) == 1)) {
            return year * 12 + month;
        } else if ((startCalendar.get(Calendar.DATE) == 1) && (temp.get(Calendar.DATE) != 1)) {
            return year * 12 + month;
        } else {
            return (year * 12 + month - 1) < 0 ? 0 : (year * 12 + month);
        }
    }

    /*获取间隔的月数*/
    public static Integer getMonthsNum(String dstr1, String dstr2) {
        try {
            SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");//小写的mm表示的是分钟
            Date date1 = sdf.parse(dstr1);
            Date date2 = sdf.parse(dstr2);
            Integer monthsNum = ZtDateUtil.getMonth(date1, date2);
            return monthsNum;
        } catch (ParseException e) {
            e.printStackTrace();
        }
        return null;
    }

    /*获取月份的第一天*/
    public static String getFirstDay(String date, Integer num) {
        SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");
        //获取前月的第一天
        Calendar cal = Calendar.getInstance();//获取当前日期
        /*对前端出入的日期进行Date格式化*/
        Date date1 = null;
        Integer count = -num;
        try {
            date1 = format.parse(date);
        } catch (ParseException e) {
            e.printStackTrace();
        }
        cal.setTime(date1);
        cal.add(Calendar.MONTH, count);
        cal.set(Calendar.DAY_OF_MONTH, 1);//设置为1号,当前日期既为本月第一天
        String firstDay = format.format(cal.getTime());
        return firstDay;
    }

    /*获取月份的最后一天*/
    public static String getLastDay(String date, Integer num) {
        SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");
        //获取前月的第一天
        Calendar cal = Calendar.getInstance();
        /*对前端出入的日期进行Date格式化*/
        Date date1 = null;
        Integer count = 1 - num;
        try {
            date1 = format.parse(date);
        } catch (ParseException e) {
            e.printStackTrace();
        }
        cal.setTime(date1);
        cal.add(Calendar.MONTH, count);
        cal.set(Calendar.DAY_OF_MONTH, 0);//设置为1号,当前日期既为本月第一天
        String lastDay = format.format(cal.getTime());
        return lastDay;
    }

    /*获取前几个月*/
    public static String getMonthsBefore(String date, Integer num) {
        SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");
        Date date1 = null;
        String beforeMonth = null;
        Calendar cale = Calendar.getInstance();
        try {
            date1 = format.parse(date);
        } catch (ParseException e) {
            e.printStackTrace();
        }
        cale.setTime(date1);
        cale.add(Calendar.MONTH, -num);
        cale.set(Calendar.DAY_OF_MONTH, 0);//设置为1号,当前日期既为本月第一天
        beforeMonth = format.format(cale.getTime());
        return beforeMonth;
    }

    /*计算自然周*/
    public static List<String> getWeekFirsLast(String date, Integer num) {
        List<String> containDays = new ArrayList<String>();
        Calendar week = Calendar.getInstance();
        SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");
        Integer count1 = 1 - num;
        try {
            week.setTime(format.parse(date));
            week.add(Calendar.WEEK_OF_YEAR, count1);
            date = format.format(week.getTime());
            Calendar c = Calendar.getInstance();
            c.setTime(format.parse(date));
            c.set(Calendar.DAY_OF_WEEK, 1);
            /*周中第一天*/
            date = format.format(c.getTime());
            containDays.add(date);
            c.set(Calendar.DAY_OF_WEEK, 7);
            /*周中最后一天*/
            date = format.format(c.getTime());
            containDays.add(date);
        } catch (ParseException e) {
            e.printStackTrace();
        }
        return containDays;
    }

    /*计算相差的周数*/
    public static Integer getcountTwoDayWeek(String startDate, String endDate) {
        SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");
        if (StringUtils.isNotEmpty(startDate) && StringUtils.isNotEmpty(endDate)) {
            Date start = null;
            Date end = null;
            try {
                start = format.parse(startDate);
                end = format.parse(endDate);
            } catch (ParseException e) {
                e.printStackTrace();
            }
            Calendar cal = Calendar.getInstance();
            cal.setTime(start);
            long time1 = cal.getTimeInMillis();
            cal.setTime(end);
            long time2 = cal.getTimeInMillis();
            long between_days = (time2 - time1) / (1000 * 3600 * 24);
            Double days = Double.parseDouble(String.valueOf(between_days));
            if ((days / 7) > 0 && (days / 7) <= 1) {
                //不满一周的按一周算
                return 1;
            } else if (days / 7 > 1) {
                int day = days.intValue();
                if (day % 7 > 0) {
                    return day / 7 + 1;
                } else {
                    return day / 7;
                }
            } else if ((days / 7) == 0) {
                return 0;
            } else {
                //负数返还null
                return null;
            }
        }
        return null;
    }
}