日期处理工具类

package utils;

import org.apache.commons.lang.time.DateUtils;

import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
import java.util.GregorianCalendar;

/**
 * Created by lightClouds917
 * Date 2018/1/9
 * Description:date util
 */
public class MyDateUtil {

    /**test those methods*/
    public static void main(String[] args) throws Exception{
        Date date = int2Date(42237);
        //Fri Aug 21 00:00:00 CST 2015
        System.out.println(int2Date(42237));
        //2015.8.21
        System.out.println(getYearOrMonthOrDay(date,"year"));
        //2015
        System.out.println(getYearOrMonthOrDay(date,"month"));
        //8
        System.out.println(getYearOrMonthOrDay(date,"day"));
        //21
        Date dateByString1 = string2Date("2017.7.1");
        System.out.println(dateByString1.toString());
        //Sat Jul 01 00:00:00 CST 2017
        System.out.println(date2String1(dateByString1));
        //2017年7月1日
        System.out.println(date2String2(dateByString1));
        //2017-7-1
        System.out.println(string2Date("2017-8-15"));
        //Tue Aug 15 00:00:00 CST 2017
        System.out.println(string2Date("2017年8月15日"));
        //Tue Aug 15 00:00:00 CST 2017
        System.out.println(getNowYear());
        //2018
        System.out.println(getNowMonth());
        //3

    }

    /**
     * int类型转为日期类
     * 一般用于解析Excel
     *
     * parse date by int
     * we use it always in parsing Excel
     * @param dateNum
     * @return
     */
    public static Date int2Date(Integer dateNum){
        Calendar calendar = new GregorianCalendar(1900,0,-1);
        Date dateRe = DateUtils.addDays(calendar.getTime(),dateNum);
        return dateRe;
    }

    /**
     * get year or month or day from date which instance of Date
     * @param date
     * @param type
     * @return
     */
    public static Integer getYearOrMonthOrDay(Date date,String type){
        Calendar calendar = Calendar.getInstance();
        calendar.setTime(date);
        if("year".equals(type)){
            return calendar.get(Calendar.YEAR);
        }else if("month".equals(type)){
            return calendar.get(Calendar.MONTH)+1;
        }else if("day".equals(type)){
            return calendar.get(Calendar.DAY_OF_MONTH);
        }
        return null;
    }

    /**
     * parse String to Date
     * @param str
     * @return
     * @throws Exception
     */
    public static Date string2Date(String str) throws Exception{
        Date date = null;
        if(str.contains("/")){
            str = str.replace("/","-");
        }else if(str.contains(".")){
            str = str.replace(".","-");
        }else if(!str.contains("日") && str.contains("年") && str.contains("月")){
            str = str.replace("年","-");
            str = str.replace("月","");
        }else if(str.contains("日") && str.contains("年") && str.contains("月")){
            str = str.replace("年","-");
            str = str.replace("月","-");
            str = str.replace("日","");
        }
        try {
            SimpleDateFormat format1 = new SimpleDateFormat("yyyy-MM-dd");
            date = format1.parse(str);
        }catch (Exception ex){
            SimpleDateFormat format2 = new SimpleDateFormat("yyyy-MM");
            date = format2.parse(str);
        }
        return date;
    }

    /**
     * parse Date to String   eg：2017年7月1日
     * @param date
     * @return
     */
    public static String date2String1(Date date){
        Calendar calendar = Calendar.getInstance();
        calendar.setTime(date);
        String str = calendar.get(Calendar.YEAR)+"年"+(calendar.get(Calendar.MONTH)+1)+"月"+calendar.get(Calendar.DAY_OF_MONTH)+"日";
        return str;
    }

    /**
     * parse Date to String   eg：2017-7-1
     * @param date
     * @return
     */
    public static String date2String2(Date date){
        Calendar calendar = Calendar.getInstance();
        calendar.setTime(date);
        String str = calendar.get(Calendar.YEAR)+"-"+(calendar.get(Calendar.MONTH)+1)+"-"+calendar.get(Calendar.DAY_OF_MONTH);
        return str;
    }

    /**
     * get now year eg:2018
     */
    public static Integer getNowYear(){
        Calendar cal = Calendar.getInstance();
        int nowYear = cal.get(Calendar.YEAR);
        return nowYear;
    }

    /**
     * get now month  eg:8
     */
    public static Integer getNowMonth(){
        Calendar cal = Calendar.getInstance();
        int nowMonth = cal.get(Calendar.MONTH) + 1;
        return nowMonth;
    }
}