java日期加减年月日

/**
　* 两个日期相减相差的月份
　* @param beginDate
　* @param endDate
　* @return
*/
public int getDifMonth(Date startDate, Date endDate) {
　　Calendar start = Calendar.getInstance();
　　Calendar end = Calendar.getInstance();
　　start.setTime(startDate);
　　end.setTime(endDate);
　　int result = end.get(Calendar.MONTH) - start.get(Calendar.MONTH);
　　int month = (end.get(Calendar.YEAR) - start.get(Calendar.YEAR)) * 12;
　　return Math.abs(month + result);
}

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<br>/**

     * 日期相加减

     * @param time

     *             时间字符串 yyyy-MM-dd HH:mm:ss

     * @param num

     *             加的数，-num就是减去

     * @return 

     *             减去相应的数量的年的日期

     * @throws ParseException

     */

    public static Date yearAddNum(Date time, Integer num) {

        //SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");

        //Date date = format.parse(time);

         

        Calendar calendar = Calendar.getInstance();

        calendar.setTime(time);

        calendar.add(Calendar.YEAR, num);

        Date newTime = calendar.getTime();

        return newTime;

    }

     

    /**

     *

     * @param time

     *           时间

     * @param num

     *           加的数，-num就是减去

     * @return

     *          减去相应的数量的月份的日期

     * @throws ParseException Date

     */

    public static Date monthAddNum(Date time, Integer num){

        //SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");

        //Date date = format.parse(time);

         

        Calendar calendar = Calendar.getInstance();

        calendar.setTime(time);

        calendar.add(Calendar.MONTH, num);

        Date newTime = calendar.getTime();

        return newTime;

    }

     

    /**

     *

     * @param time

     *           时间

     * @param num

     *           加的数，-num就是减去

     * @return

     *          减去相应的数量的天的日期

     * @throws ParseException Date

     */

    public static Date dayAddNum(Date time, Integer num){

        //SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");

        //Date date = format.parse(time);

         

        Calendar calendar = Calendar.getInstance();

        calendar.setTime(time);

        calendar.add(Calendar.DAY_OF_MONTH, num);

        Date newTime = calendar.getTime();

        return newTime;

    }

/** * 获取本月第一天时间 */public static Date getMonthStartDate(){    Calendar calendar = Calendar.getInstance();    calendar.set(Calendar.DAY_OF_MONTH,1);    return calendar.getTime();}/** * 获取本月最后一天 *  */public static Date getMonthEndDate(){    Calendar calendar = Calendar.getInstance();    calendar.set(Calendar.DAY_OF_MONTH, calendar.getActualMaximum(Calendar.DAY_OF_MONTH));    return calendar.getTime();}

/** * 获取本周的开始时间 */public static Date getBeginWeekDate(){    Calendar cal = Calendar.getInstance();    cal.setTime(new Date());    int dayofweek = cal.get(Calendar.DAY_OF_WEEK);    //周日是1 ，周一是 2 ，周二是 3    //所以，当周的第一天 = 当前日期 - 距离周一过了几天（周一过了0天，周二过了1天，   周日过了6天）    // 2 - 周一的（dayofweek：2 ）= 0    // 2 - 周二的（dayofweek：3 ）= -1    //                      .    //                      .    // 2 - 周日的（dayofweek：1） = 1（这个是不符合的需要我们修改）===》2 - 周日的（dayofweek：1 ==》8 ） = -6    if (dayofweek == 1) {        dayofweek += 7;    }    cal.add(Calendar.DATE, 2 - dayofweek);    return cal.getTime();}

/** * 本周的结束时间 * 开始时间 + 6天 */public static Date getEndWeekDate(){    Calendar cal = Calendar.getInstance();    cal.setTime(new Date());    int dayofweek = cal.get(Calendar.DAY_OF_WEEK);    if (dayofweek == 1) {        dayofweek += 7;    }    cal.add(Calendar.DATE, 8 - dayofweek);//2 - dayofweek + 6    return cal.getTime();}