2021-01-26 获取指定日期所在年/月/周中的第一天、最后一天、某天

整合hutool

    cn.hutool
    hutool-all
    5.4.0

---

测试

package cn.mb.test;

import cn.hutool.core.date.DateTime;
import cn.hutool.core.date.DateUnit;
import cn.hutool.core.date.DateUtil;
import cn.hutool.core.date.Week;
import cn.mb.util.DateTimeUtil;

/**
 * 

 *  DateUtil测试类
 * 
 *
 * @author: bb
 * @createDate: 2021/1/26
 */
public class DateUtilTest {
     
    public static void main(String[] args) {
     
        //  当前日期
        DateTime today = DateUtil.date();
        DateTime yesterday1 = DateUtil.yesterday();
        DateTime yesterday2 = DateUtil.offsetDay(today, -1);
        System.out.println("昨天：" + yesterday1 + "， " + yesterday2);
        DateTime tomorrow1 = DateUtil.tomorrow();
        DateTime tomorrow2 = DateUtil.offsetDay(today, 1);
        System.out.println("明天：" + tomorrow1 + "， " + tomorrow2);
        DateTime lastWeekToday1 = DateUtil.lastWeek();
        DateTime lastWeekToday2 = DateUtil.offsetWeek(today, -1);
        System.out.println("上周今天：" + lastWeekToday1 + "， " + lastWeekToday2);
        DateTime lastMonthToday1 = DateUtil.lastMonth();
        DateTime lastMonthToday2 = DateUtil.offsetMonth(today, -1);
        System.out.println("上月今天：" + lastMonthToday1 + "， " + lastMonthToday2);
        DateTime beginOfYear = DateUtil.beginOfYear(today);
        System.out.println("年第一天：" + beginOfYear);
        DateTime endOfYear = DateUtil.endOfYear(today);
        System.out.println("年最后一天：" + endOfYear);
        DateTime beginOfMonth = DateUtil.beginOfMonth(today);
        System.out.println("月第一天：" + beginOfMonth);
        DateTime endOfMonth = DateUtil.endOfMonth(today);
        System.out.println("月最后一天：" + endOfMonth);
        DateTime beginOfWeek = DateUtil.beginOfWeek(today);
        System.out.println("周第一天：" + beginOfWeek);
        DateTime endOfWeek = DateUtil.endOfWeek(today);
        System.out.println("周最后一天：" + endOfWeek);
        DateTime dayOfWeek = DateTimeUtil.getDayOfWeek(today, Week.FRIDAY);
        System.out.println("周某天：" + dayOfWeek);
        DateTime dayOfMonth = DateTimeUtil.getDayOfMonth(today, 15);
        System.out.println("月某天：" + dayOfMonth);
        DateTime dayOfYear = DateTimeUtil.getDayOfYear(today, 150);
        System.out.println("年某天：" + dayOfYear);

        //  时间差
        long 天数差 = DateUtil.between(DateUtil.yesterday(), DateUtil.tomorrow(), DateUnit.DAY);
        System.out.println("天数差：" + 天数差);
        long 小时差 = DateUtil.between(DateUtil.yesterday(), DateUtil.tomorrow(), DateUnit.HOUR);
        System.out.println("小时差：" + 小时差);

        //  判断闰年
        boolean isLeapYear = DateUtil.isLeapYear(2021);
        System.out.println("2021是否为闰年：" + isLeapYear);
    }
}

---

DateTimeUtil

package cn.mb.util;

import cn.hutool.core.date.DateTime;
import cn.hutool.core.date.DateUtil;
import cn.hutool.core.date.Month;
import cn.hutool.core.date.Week;
import cn.hutool.core.util.ObjectUtil;

/**
 * 

 *  日期工具类
 * 
 *
 * @author: bb
 * @createDate: 2021/1/25
 */
public class DateTimeUtil {
     

    /**
     * 

     * 获取指定日期所在周的周几日期(周日至周六 == 1至7)
     * 
     *
     * @param date 指定日期
     * @param day  周几
     * @return cn.hutool.core.date.DateTime 日期
     * @author guohaibin
     * @date 2021-01-26 11:17:13
     */
    public static DateTime getDayOfWeek(DateTime date, Week day) {
     
        if (ObjectUtil.isNull(date) || ObjectUtil.isNull(day))
            throw new IllegalArgumentException("date or day is null");
        Week dateWeek = date.dayOfWeekEnum();
        if (dateWeek == day) return date;
        if (day == Week.MONDAY) return DateUtil.beginOfWeek(date);
        if (day == Week.SUNDAY) return DateUtil.endOfWeek(date);
        return DateUtil.offsetDay(date, day.getValue() - dateWeek.getValue());
    }

    /**
     * 

     * 获取指定日期所在月中的第几天(0-31)
     * 
     *
     * @param date 指定日期
     * @param day  第几天(0~31，0代表该月最后一天)
     * @return cn.hutool.core.date.DateTime 日期
     * @author guohaibin
     * @date 2021-01-26 11:40:34
     */
    public static DateTime getDayOfMonth(DateTime date, int day) {
     
        if (ObjectUtil.isNull(date))
            throw new IllegalArgumentException("date is null");
        if (day < 0 || day > 31)
            throw new IllegalArgumentException("day is between 0 and 31");
        Month month = date.monthEnum();
        int totalDayOfMonth = month.getLastDay(date.isLeapYear());
        if (day > totalDayOfMonth) {
     
            throw new IllegalArgumentException(totalDayOfMonth + " days at most in " + month);
        }
        if (date.dayOfMonth() == day) return date;
        if (day == 0) return DateUtil.endOfMonth(date);
        if (day == 1) return DateUtil.beginOfMonth(date);
        return DateUtil.offsetDay(date, day - date.dayOfMonth());
    }

    /**
     * 

     * 获取指定日期所在年中的第几天(0-366)
     * 
     *
     * @param date 指定日期
     * @param day  第几天(0~366，0代表该年最后一天)
     * @return cn.hutool.core.date.DateTime 日期
     * @author guohaibin
     * @date 2021-01-26 11:40:34
     */
    public static DateTime getDayOfYear(DateTime date, int day) {
     
        if (ObjectUtil.isNull(date))
            throw new IllegalArgumentException("date is null");
        if (day < 0 || day > 366)
            throw new IllegalArgumentException("day is between 0 and 366");
        int lengthOfYear = DateUtil.lengthOfYear(date.year());
        if (day > lengthOfYear) {
     
            throw new IllegalArgumentException(lengthOfYear + " days at most in " + date.year());
        }
        if (day == 1) return DateUtil.beginOfYear(date);
        if (day == 0) return DateUtil.endOfYear(date);
        return DateUtil.offsetDay(date, day - date.dayOfYear());
    }

}