计算两个日期之间的差： 两个变量 d1，d2 例：d1="2018-05-16" , d2="2019-08-07" public static int getMonthDiff(String d1, String d2){
     try {
        SimpleDateFormat sdf = new SimpleDateFormat("yyyyMM");       Calendar c1 = Calendar.getInstance();       Calendar c2 = Calendar.getInstance();       c1.setTime(sdf.parse(d1));       c2.setTime(sdf.parse(d2));       if(c1.getTimeInMillis() < c2.getTimeInMillis()) {
           return 0;       }       int year1 = c1.get(Calendar.YEAR);       int year2 = c2.get(Calendar.YEAR);       int month1 = c1.get(Calendar.MONTH);       int month2 = c2.get(Calendar.MONTH);       int day1 = c1.get(Calendar.DAY_OF_MONTH);       int day2 = c2.get(Calendar.DAY_OF_MONTH);       int yearInterval = year1 - year2;       // 如果 d1的 月-日 小于 d2的 月-日 那么 yearInterval-- 这样就得到了相差的年数       if(month1 < month2 || month1 == month2 && day1 < day2) yearInterval --;       // 获取月数差值       int monthInterval =  (month1 + 12) - month2  ;       if(day1 < day2) monthInterval --;       monthInterval %= 12;       return yearInterval * 12 + monthInterval;    } catch (ParseException e) {
        e.printStackTrace();    }    return 0; }