DateTimeUtil

 <dependency>
      <groupId>joda-timegroupId>
      <artifactId>joda-timeartifactId>
      <version>2.3version>
dependency>

package com.mark.util;

import org.apache.commons.lang3.StringUtils;
import org.joda.time.DateTime;
import org.joda.time.format.DateTimeFormat;
import org.joda.time.format.DateTimeFormatter;

import java.util.Calendar;
import java.util.Date;

/**
 * Created by Mark on 2018/3/26.
 */
public class DateTimeUtil {
    public static final String STANDARD_FORMAT = "yyyy-MM-dd HH:mm:ss";
    public static final String STANDARD_FORMAT2 = "yyyy-MM-dd";

    public static Date strToDate(String dateTimeStr, String formatStr){
        DateTimeFormatter dateTimeFormatter = DateTimeFormat.forPattern(formatStr);
        DateTime dateTime = dateTimeFormatter.parseDateTime(dateTimeStr);
        return dateTime.toDate();
    }

    public static String dateToStr(Date date,String formatStr){
        if(date == null){
            return StringUtils.EMPTY;
        }
        DateTime dateTime = new DateTime(date);
        return dateTime.toString(formatStr);
    }

    public static Date strToDate(String dateTimeStr){
        DateTimeFormatter dateTimeFormatter = DateTimeFormat.forPattern(STANDARD_FORMAT);
        DateTime dateTime = dateTimeFormatter.parseDateTime(dateTimeStr);
        return dateTime.toDate();
    }

    public static String dateToStr(Date date){//返回的时间格式是年月日时分秒
        if(date == null){
            return StringUtils.EMPTY;
        }
        DateTime dateTime = new DateTime(date);
        return dateTime.toString(STANDARD_FORMAT);
    }
    public static String dateToStr2(Date date){ //返回的时间格式是年月日
        if(date == null){
            return StringUtils.EMPTY;
        }
        DateTime dateTime = new DateTime(date);
        return dateTime.toString(STANDARD_FORMAT2);
    }

    public static int dayBetween(Date date1 ,  Date date2 ){
        Calendar calendar = Calendar.getInstance();
        calendar.setTime(date1);
        long time1 = calendar.getTimeInMillis();
        calendar.setTime(date2);
        long time2 = calendar.getTimeInMillis();
        long  between_days=(time2-time1)/(1000*3600*24);
        return Integer.parseInt(String.valueOf(between_days));
    }

    public static void main(String[] args){
        String time =  DateTimeUtil.dateToStr2(new Date());
        System.out.println(time);
    }
}