如何使用Hutool工具类中DateUtil呢?

1、Date、long、Calendar之间的相互转换

    //当前时间
    Date date = DateUtil.date();
    //当前时间
    Date date2 = DateUtil.date(Calendar.getInstance());
    //当前时间
    Date date3 = DateUtil.date(System.currentTimeMillis());
    //当前时间字符串，格式：yyyy-MM-dd HH:mm:ss
    String now = DateUtil.now();
    //当前日期字符串，格式：yyyy-MM-dd
    String today= DateUtil.today();

2、字符串转日期

DateUtil.parse方法会自动识别一些常用格式
  包括： 
yyyy-MM-dd HH:mm:ss

    yyyy/MM/dd HH:mm:ss
    yyyy.MM.dd HH:mm:ss
    yyyy年MM月dd日 HH时mm分ss秒
    yyyy-MM-dd
    yyyy/MM/dd
    yyyy.MM.dd
    HH:mm:ss
    HH时mm分ss秒
    yyyy-MM-dd HH:mm
    yyyy-MM-dd HH:mm:ss.SSS
    yyyyMMddHHmmss
    yyyyMMddHHmmssSSS
    yyyyMMdd
    EEE, dd MMM yyyy HH:mm:ss z
    EEE MMM dd HH:mm:ss zzz yyyy
    yyyy-MM-dd'T'HH:mm:ss'Z'
    yyyy-MM-dd'T'HH:mm:ss.SSS'Z'
    yyyy-MM-dd'T'HH:mm:ssZ
    yyyy-MM-dd'T'HH:mm:ss.SSSZ

    String dateStr = "2024-03-01";
    Date date1 = DateUtil.parse(dateStr);
    Date date2 = DateUtil.parse(dateStr, "yyyy-MM-dd");

3、格式化日期输出

    String dateStr = "2024-03-01";
    Date date = DateUtil.parse(dateStr);
     
    //结果 2024/03/01
    String format = DateUtil.format(date, "yyyy/MM/dd");
     
    //常用格式的格式化，结果：2024-03-01
    String formatDate = DateUtil.formatDate(date);
     
    //结果：2024-03-01 00:00:00
    String formatDateTime = DateUtil.formatDateTime(date);
     
    //结果：00:00:00
    String formatTime = DateUtil.formatTime(date);

4、获取Date对象的某个部分

    Date date = DateUtil.date();
    //获得年的部分
    DateUtil.year(date);
    //获得月份，从0开始计数,实际需要加1
    DateUtil.month(date);
    //获得月份枚举
    DateUtil.monthEnum(date)
    //获取天
    DateUtil.dayOfMonth(date)
    //获取时
    DateUtil.hour(date, true);
    //获取分
    DateUtil.minute(date);
    //获取秒
    DateUtil.second(date);

5、开始和结束时间

    String dateStr = "2024-03-01 22:43:13";
    Date date = DateUtil.parse(dateStr);
    //获取日开始和结束
    Date beginOfDay = DateUtil.beginOfDay(date);
    Date endOfDay = DateUtil.endOfDay(date);
    //获取周开始和结束
    DateTime beginOfWeek= DateUtil.beginOfWeek(date);
    DateTime endOfWeek= DateUtil.endOfWeek(date);
    //获取月开始和结束
    DateTime beginOfMonth= DateUtil.beginOfMonth(date);
    DateTime endOfMonth= DateUtil.endOfMonth(date);
    //获取季度开始和结束
    DateTime beginOfQuarter= DateUtil.beginOfQuarter(date);
    DateTime endOfQuarter= DateUtil.endOfQuarter(date);
    //获取年开始和结束
    DateTime beginOfYear = DateUtil.beginOfYear(date);
    DateTime endOfYear= DateUtil.endOfYear(date);

6、日期时间偏移

 
    String dateStr = "2024-03-01 22:33:23";
    Date date = DateUtil.parse(dateStr);
     
    //结果：2024-03-03 22:33:23
    Date newDate = DateUtil.offset(date, DateField.DAY_OF_MONTH, 2);
     
    //常用偏移，结果：2024-03-04 22:33:23
    DateTime newDate2 = DateUtil.offsetDay(date, 3);
     
    //常用偏移，结果：2024-03-01 19:33:23
    DateTime newDate3 = DateUtil.offsetHour(date, -3);

    //昨天
    DateUtil.yesterday()
    //明天
    DateUtil.tomorrow()
    //上周
    DateUtil.lastWeek()
    //下周
    DateUtil.nextWeek()
    //上个月
    DateUtil.lastMonth()
    //下个月
    DateUtil.nextMonth()

7、日期时间差

有时候我们需要计算两个日期之间的时间差（相差天数、相差小时数等等），Hutool将此类方法封装为between方法：

    String dateStr1 = "2024-08-01 20:13:43";
    Date date1 = DateUtil.parse(dateStr1);
     
    String dateStr2 = "2024-07-01 20:13:23";
    Date date2 = DateUtil.parse(dateStr2);
     
    //相差一个月，31天
    long betweenDay = DateUtil.between(date1, date2, DateUnit.DAY);

有时候我们希望看到易读的时间差，比如XX天XX小时XX分XX秒，此时使用DateUtil.formatBetween方法：

    //Level.SECOND表示精确到秒
    DateUtil.formatBetween(dateTime1, dateTime2, BetweenFormatter.Level.SECOND);

不然原始方法计算两个时间差如下:

    public static String timeDistance(Date endTime, Date startTime) {
            long nd = 1000 * 24 * 60 * 60;
            long nh = 1000 * 60 * 60;
            long nm = 1000 * 60;
            long ns = 1000;
            // 获得两个时间的毫秒时间差异
            long diff = endTime.getTime() - startTime.getTime();
            // 计算差多少天
            long day = diff / nd;
            // 计算差多少小时
            long hour = diff % nd / nh;
            // 计算差多少分钟
            long min = diff % nd % nh / nm;
            // 计算差多少秒//输出结果
            long sec = diff % nd % nh % nm / ns;
            String str = "";
            if (day > 0) {
                str += day + "天";
            }
            if (hour > 0) {
                str += hour + "小时";
            }
            if (min > 0) {
                str += min + "分钟";
            }
            if (sec > 0) {
                str += sec + "秒";
            }
            return str;
        }

8、星座和属相

    // "摩羯座",注意月份不能直接用int数值
    String zodiac = DateUtil.getZodiac(Month.JANUARY.getValue(), 19);
     
    // "狗"
    String chineseZodiac = DateUtil.getChineseZodiac(1994);

9、其他

    //年龄
    DateUtil.ageOfNow("1990-01-30");
     
    //是否闰年
    DateUtil.isLeapYear(2024);
     
    Date date = DateUtil.date();
    //计算日期是一年当中第几天
    DateUtil.dayOfYear(date );
    //计算日期是周几,从0开始，实际要加1
    DateUtil.weekOfMonth(date);
    //计算日期是一年当中的第几周
    DateUtil.weekOfYear(date);
    //计算日期属于第几季度
    DateUtil.quarter(date);
     
     
    //获取两个日期中间所有日期，包含开始和结束
    public static list<String> rangeDay(DateTime start, DateTime end){
            List<String> dates = new LinkedList<>();
            DateTime currentDate = start;
            while (!currentDate.isAfter(end)) {
                dates.add(DateUtil.format(currentDate,"yyyyMMdd"));
                currentDate = currentDate.offset(DateField.DAY_OF_MONTH,1);
            }
            return dates;
        }
     
    //获取两个日期中间所有月份，包含开始和结束
    public static List<String> rangeMonth(DateTime start, DateTime end){
            List<String> dates = new LinkedList<>();
            DateTime currentDate = start;
            while (!currentDate.isAfter(end)) {
                dates.add(DateUtil.format(currentDate,"yyyyMM"));
                currentDate = currentDate.offset(DateField.MONTH,1);
            }
            return dates;
        }
     
     
    //获取两个日期中间所有年份，包含开始和结束
    public static List<String> rangeMonth(DateTime start, DateTime end){
            List<String> dates = new LinkedList<>();
            DateTime currentDate = start;
            while (!currentDate.isAfter(end)) {
                dates.add(DateUtil.format(currentDate,"yyyy"));
                currentDate = currentDate.offset(DateField.YEAR,1);
            }
            return dates;
        }