The use of DateUtil (date and time tool) in the Hutool tool set

The use of DateUtil (date and time tool) in the Hutool tool set

1 Overview

The date and time package is one of the core packages of Hutool, which provides encapsulation for Date and Calendar objects in JDK, and DateUtil provides a series of static methods for date and time operations.

2. Commonly used methods

2-1) Mutual conversion between Date, long and Calendar

public static void main(String[] args) {
    
    
        //当前时间:date = 2019-09-17 16:59:23
        Date date = DateUtil.date();

        //当前时间:date2 = 2019-09-17 16:59:23
        Date date2 = DateUtil.date(Calendar.getInstance());

        //当前时间:date3 = 2019-09-17 16:59:23
        Date date3 = DateUtil.date(System.currentTimeMillis());

        //当前时间字符串:now = 2019-09-17 16:59:23
        String now = DateUtil.now();

        //当前日期字符串:today = 2019-09-17
        String today= DateUtil.today();
    }

2-2) Convert string to date

/*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
yyyy-MM-dd HH:mm:ss.SSS*/

//这四种情况均可以转换，并且输出结果均为： 2019-09-17 00:00:00
Date date1 = DateUtil.parse("2019-09-17");
Date date2 = DateUtil.parse("2019-09-17", "yyyy-MM-dd");
Date date3 = DateUtil.parse("2019/09/17", "yyyy/MM/dd");
Date date4 = DateUtil.parse("2019:09:17", "yyyy:MM:dd");

2-3) Format date output

Date date1 = DateUtil.parse("2019-09-17");

//结果: 2019/09/17
String format = DateUtil.format(date1, "yyyy/MM/dd");

//常用格式的格式化，结果：2017-03-01
String formatDate = DateUtil.formatDate(date1);

//结果：2019-09-17 00:00:00
String formatDateTime = DateUtil.formatDateTime(date1);

//结果：00:00:00
String formatTime = DateUtil.formatTime(date1);

2-4) Get a certain part of the Date object

Date date = DateUtil.date();

//获得年的部分:year = 2019
int year = DateUtil.year(date);

//获得月份，从0开始计数:month = 8
int month = DateUtil.month(date);

//获得月份枚举 :monthEnum = SEPTEMBER
Month monthEnum = DateUtil.monthEnum(date);

2-5) Start and end time

String now = DateUtil.now();
Date date = DateUtil.parse(now);

//一天的开始，结果：2019-09-17 00:00:00
Date beginOfDay = DateUtil.beginOfDay(date);

//一天的结束，结果：2019-09-17 23:59:59
Date endOfDay = DateUtil.endOfDay(date);

//一个月的开始
Date beginDate = DateUtil.beginOfMonth(date);

//一个月的结束
Date endDate = DateUtil.endOfMonth(date);

2-6) Date and time offset

String now = DateUtil.now();

//date = 2019-09-17 17:35:35
Date date = DateUtil.parse(now);

//结果：newDate = 2019-09-19 17:35:35
Date newDate = DateUtil.offset(date, DateField.DAY_OF_MONTH, 2);

//常用偏移，结果：newDate2 = 2019-09-20 17:35:35
DateTime newDate2 = DateUtil.offsetDay(date, 3);

//常用偏移，结果：newDate3 = 2019-09-17 14:35:35
DateTime newDate3 = DateUtil.offsetHour(date, -3);

//针对当前时间，提供了简化的偏移方法（例如昨天、上周、上个月等）：
//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()

2-7) Date and time difference

Date date1 = DateUtil.parse("2019-09-20 17:35:35");
Date date2 = DateUtil.parse("2019-09-17 14:35:35");

//这里若date1和date2换位置，输出结果不变：betweenDay = 3
long betweenDay = DateUtil.between(date1, date2, DateUnit.DAY);

2-8) Others

//年龄：ageOfNow = 28
int ageOfNow = DateUtil.ageOfNow("1991-01-13");

//是否闰年：leapYear = false
boolean leapYear = DateUtil.isLeapYear(2019);