计算两个日期月份差，不足一月按0月算，时间不参与计算

/**
     * 计算两个日期月份差，不足一月按0月算，
     * 日期没有前后顺序，时间不参与计算
     * getMonthSub 2019.12.22 00:00:00  2019.12.23 00:00:00 0
     * getMonthSub 2019.11.23 00:00:00  2019.12.22 00:00:00 0
     * getMonthSub 2019.12.23 00:00:00  2020.12.22 00:00:00 11
     * getMonthSub 2018.11.02 00:00:00  2019.02.03 00:00:00 3
     * getMonthSub 2018.11.02 00:00:00  2019.02.01 00:00:00 2
     *
     * getMonthSub 2019.12.23 00:00:00  2019.12.22 00:00:00 0
     * getMonthSub 2019.12.22 00:00:00  2019.11.23 00:00:00 0
     * getMonthSub 2020.12.22 00:00:00  2019.12.23 00:00:00 11
     * getMonthSub 2019.02.03 00:00:00  2018.11.02 00:00:00 3
     * getMonthSub 2019.02.01 00:00:00  2018.11.02 00:00:00 2
     * @param time1     时间1
     * @param time2     时间2
     * @param format    时间格式
     * @return
     */
    public static int getMonthSub(String time1,String time2,String format)throws Exception{
        SimpleDateFormat sdf = new SimpleDateFormat(format);
        Calendar before = Calendar.getInstance();
        Calendar after = Calendar.getInstance();
        Date beforeDate = sdf.parse(time1);
        Date afterDate = sdf.parse(time2);
        if(beforeDate.compareTo(afterDate)>0){
            before.setTime(afterDate);
            after.setTime(beforeDate);
        }else if(beforeDate.compareTo(afterDate)<0){
            before.setTime(beforeDate);
            after.setTime(afterDate);
        }else{
            return 0;
        }
        int surplus = after.get(Calendar.DATE) - before.get(Calendar.DATE);
        int result = after.get(Calendar.MONTH) - before.get(Calendar.MONTH);
        int month = (after.get(Calendar.YEAR) - before.get(Calendar.YEAR)) * 12;
        surplus = surplus < 0 ? -1 : 0;
        return  Math.abs(month + result) + surplus;
    }

public static void main(String[] args){
    try {
            System.out.println("getMonthSub 2019.12.22 00:00:00  2019.12.23 00:00:00 " + getMonthSub("2019.12.22 00:00:00", "2019.12.23 00:00:00", "yyyy.MM.dd HH:mm:ss"));//0
            System.out.println("getMonthSub 2019.11.23 00:00:00  2019.12.22 00:00:00 " + getMonthSub("2019.11.23 00:00:00", "2019.12.22 00:00:00", "yyyy.MM.dd HH:mm:ss"));//0
            System.out.println("getMonthSub 2019.12.23 00:00:00  2020.12.22 00:00:00 " + getMonthSub("2019.12.23 00:00:00", "2020.12.22 00:00:00", "yyyy.MM.dd HH:mm:ss"));//11
            System.out.println("getMonthSub 2018.11.02 00:00:00  2019.02.03 00:00:00 " + getMonthSub("2018.11.02 00:00:00", "2019.02.03 00:00:00", "yyyy.MM.dd HH:mm:ss"));//3
            System.out.println("getMonthSub 2018.11.02 00:00:00  2019.02.01 00:00:00 " + getMonthSub("2018.11.02 00:00:00", "2019.02.01 00:00:00", "yyyy.MM.dd HH:mm:ss"));//2
            System.out.println();
            System.out.println("getMonthSub 2019.12.23 00:00:00  2019.12.22 00:00:00 " + getMonthSub("2019.12.23 00:00:00", "2019.12.22 00:00:00", "yyyy.MM.dd HH:mm:ss"));//0
            System.out.println("getMonthSub 2019.12.22 00:00:00  2019.11.23 00:00:00 " + getMonthSub("2019.12.22 00:00:00", "2019.11.23 00:00:00", "yyyy.MM.dd HH:mm:ss"));//0
            System.out.println("getMonthSub 2020.12.22 00:00:00  2019.12.23 00:00:00 " + getMonthSub("2020.12.22 00:00:00", "2019.12.23 00:00:00", "yyyy.MM.dd HH:mm:ss"));//11
            System.out.println("getMonthSub 2019.02.03 00:00:00  2018.11.02 00:00:00 " + getMonthSub("2019.02.03 00:00:00", "2018.11.02 00:00:00", "yyyy.MM.dd HH:mm:ss"));//3
            System.out.println("getMonthSub 2019.02.01 00:00:00  2018.11.02 00:00:00 " + getMonthSub("2019.02.01 00:00:00", "2018.11.02 00:00:00", "yyyy.MM.dd HH:mm:ss"));//2
        }catch (Exception e){
            e.printStackTrace();
        }
}