java计算两个日期相差月数

1.计算两个日期相差月数，不满一月按一月算

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.List;
 
 public static void main(String[] args) throws ParseException {
        System.out.println(getMonthSpace("2020-09-29", "2020-10-27"));

    }

/**
  * 获取两个日期相差多少个月
  */

    public static int getMonthSpace(String date1, String date2)
            throws ParseException {

        int result = 0;

        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");

        Calendar c1 = Calendar.getInstance();
        Calendar c2 = Calendar.getInstance();

        c1.setTime(sdf.parse(date1));
        c2.setTime(sdf.parse(date2));

      int i = c2.get(Calendar.YEAR)-c1.get(Calendar.YEAR);
        int month = 0;
        if (i<0)
        {
            month = -i*12;
        }else if(i>0)
        {
            month =  i*12;
        }
        result = (c2.get(Calendar.MONDAY) - c1.get(Calendar.MONTH)) + month;
        
        return result == 0 ? 1 : Math.abs(result);

    }

2.sql语句计算两个日期时间差

select now()  获取当前日期  年月日 时分秒
select curdate()  获取当前日期  只有年月日
select curtime() 获取当前日期  只有时分秒

计算两个指定日期的月差

SELECT TIMESTAMPDIFF(month,'2020-02-29','2020-04-01') AS DiffDate

计算指定日期与当前日期月差

 SELECT TIMESTAMPDIFF(month,'2020-02-28',(select curdate())) AS DiffDate

计算天的

SELECT DATEDIFF('2008-12-29','2008-12-28') AS DiffDate

记录一个方法

			Date creditDate = new Date();
                //格式化日期的对象(转化成习惯的时间格式)
            SimpleDateFormat formatter= new SimpleDateFormat("yyyy-MM-dd");
            String date_out = formatter.format(creditDate).toString();
           

formatter.format（）这个方法可以将日期转换为指定格式
像 Sun Feb 28 00:00:00 CST 2020 这样格式也可以进行转换

十二个月的日期
SELECT a.price,b.time2 from  
(select original_value as price,FROM_UNIXTIME( UNIX_TIMESTAMP(c.create_time),'%m' ) as mon 
from asset_info c where  FROM_UNIXTIME( UNIX_TIMESTAMP(c.create_time),'%Y' ) = '2020' GROUP BY mon) a 
RIGHT JOIN (SELECT '01' as time2 from  DUAL UNION ALL  
SELECT '02' as time2 from  DUAL UNION ALL 
SELECT '03' as time2 from  DUAL UNION ALL 
SELECT '04' as time2 from  DUAL UNION ALL 
SELECT '05' as time2 from  DUAL UNION ALL 
SELECT '06' as time2 from  DUAL UNION ALL 
SELECT '07' as time2 from  DUAL UNION ALL 
SELECT '08' as time2 from  DUAL UNION ALL 
SELECT '09' as time2 from  DUAL UNION ALL 
SELECT '10' as time2 from  DUAL UNION ALL 
SELECT '11' as time2 from  DUAL UNION ALL 
SELECT '12' as time2 from  DUAL )b on a.mon = b.time2