JDK时间类

1.Date类

//创建对象表示当前时间
Date d1 = new Date();
System.out.println(d1);
//创建对象表示一个指定的时间
Date d2 = new Date(0L);
System.out.println(d2);//Thu Jan 01 08:00:00 CST 1970
//settime设置时间
//1000毫秒 = 1秒
d1.setTime(1000l);//Thu Jan 01 08:00:01 CST 1970
System.out.println(d1);

• 打印时间原点一年以后的时间

private static void extracted() {
    Date d1 = new Date(0);
    System.out.println(d1);//Thu Jan 01 08:00:00 CST 1970
    long time = d1.getTime();
    time = time + 1000l*60*60*24*365;
    d1.setTime(time);
    System.out.println(d1);//Fri Jan 01 08:00:00 CST 1971
}

• 定义任意两个date对象，比较哪个时间在前，哪个时间在后

private static void max() {
    Random r = new Random();
    Date date01 = new Date(Math.abs(r.nextInt()));
    Date date02 = new Date(Math.abs(r.nextInt()));
    System.out.println(date01);
    System.out.println(date02);
    long time01 = date01.getTime();
    long time02 = date02.getTime();
    if (time01 > time02) {
        System.out.println("time01 > time02");

    }else  {
        System.out.println("time01 < time02");
    }
}

1.1 ZoodID

//1.获取Java中支持的所有时区
Set<String> ZoneIds = ZoneId.getAvailableZoneIds();
System.out.println(ZoneIds);
//2.获取系统默认时区
ZoneId zoneId1 = ZoneId.systemDefault();
System.out.println(zoneId1);
//3.获取一个指定时区
ZoneId zoneId = ZoneId.of("Asia/Shanghai");
System.out.println(zoneId);

1.2 Istant

 //1.获取当前的时间Instant对象
    Instant instant = Instant.now();
    System.out.println(instant);
    //2.根据（秒/毫秒/纳秒)获取Instant对象
    Instant instant1 = Instant.ofEpochMilli(1000l);//根据毫秒获取对象
    System.out.println(instant1);
    Instant instant2 = Instant.ofEpochSecond(1l);//根据秒获取对象
    System.out.println(instant2);//根据秒和纳秒获取对象
    Instant instant3 = Instant.ofEpochSecond(2l, 1000000000l);
    System.out.println(instant3);
    //3.获取指定时区的时间
    ZonedDateTime zonedDateTime = Instant.now().atZone(ZoneId.of("Asia/Shanghai"));
    System.out.println(zonedDateTime);
    //isBefore 判断是否在前面
    Instant instant4 = Instant.ofEpochMilli(100l);
    Instant instant5 = Instant.ofEpochSecond(1l);
    boolean result = instant4.isBefore(instant5);
    System.out.println(result);
    //isAfter  判断是否在后面
    boolean result1 = instant4.isAfter(instant5);
    System.out.println(result);
    //4.minusXxx 减少时间系列的方法
    Instant instant7 = Instant.ofEpochSecond(3l);//1970-01-01T00:00:03Z
    Instant instant8 = instant7.minusSeconds(1);
    System.out.println(instant8);//1970-01-01T00:00:02Z
    //5.plusXxx 增加时间系列的方法
    Instant instant9 = instant8.plusSeconds(1);
    System.out.println(instant9);
}

1.3 ZoneDatetime

public static void main(String[] args) {
    //1.获得当前时间的ZoneDateTime对象（带时区）
    ZonedDateTime now = ZonedDateTime.now();
    System.out.println(now);//2026-01-23T14:36:48.289692100+08:00[Asia/Shanghai]
    //2.获得指定时间的ZoneDatetime对象（带时区）
    //按年月日时分秒纳秒时区指定
    ZonedDateTime.of(2026,6,16,23,23,
            22,23, ZoneId.of("Asia/Shanghai"));
    //3.通过Instant＋时区的方法获取指定事件对象
    Instant instant = Instant.ofEpochMilli(0l);
    ZoneId zoneId = ZoneId.of("Asia/Shanghai");
    System.out.println(ZonedDateTime.ofInstant(instant, zoneId));//1970-01-01T08:00+08:00[Asia/Shanghai]
   //4.withXxx 修改时间系列的方法
    ZonedDateTime zonedDateTime = now.withYear(2000);
    System.out.println(zonedDateTime);//2000-01-23T14:48:58.668346200+08:00[Asia/Shanghai]
    //减少时间系列的方法
    ZonedDateTime zonedDateTime1 = zonedDateTime.minusDays(1);
    System.out.println(zonedDateTime1);//2000-01-22T14:54:56.174043700+08:00[Asia/Shanghai]
    //增加时间系列的方法
    ZonedDateTime zonedDateTime2 = zonedDateTime.plusDays(1);
    System.out.println(zonedDateTime2);//2000-01-24T14:54:56.174043700+08:00[Asia/Shanghai]
}
/*jdk8出现的时间对象都是不可改变的
如果我们修改 增加或者减少
调用者是不会发生改变的 只会产生新的时间对象
 */

2.Calender(日历类)

       public static void main(String[] args) {
        /*1.获取日历对象
        细节1.
        Calendar是一个抽象类  不能直接new出来 需要用静态方法获取到子类对象
        底层原理：会根据系统的不同时区获取不同的日历对象，默认为当前时间
        会把时间中的纪元，年，月，日，时，分，秒都放进一个数组中
        细节2.
        月份:范围0~11 如果获取的是0实际上得到的是一月
        星期：在老外眼里星期日就是一周中的第一天 1（星期天） 2（星期一）
         */
        Calendar c = Calendar.getInstance();
        System.out.println(c.getTime());
        // Date d = new Date(0l);
        // c.setTime(d);
        long timeInMillis = c.getTimeInMillis();//拿到时间毫秒值
        c.setTimeInMillis(0l);//给日历对象设置时间毫秒值
        System.out.println(c.getTime());//Fri Jan 23 14:01:44 CST 2026
        c.set(Calendar.HOUR_OF_DAY,0);//修理日历中某的字段的信息
        c.add(Calendar.DAY_OF_MONTH,1);//为某个字段的信息增加或减少指定的值
        int year = c.get(Calendar.YEAR);
        int month = c.get(Calendar.MONTH)+1;
        int day = c.get(Calendar.DAY_OF_MONTH);
        int week = c.get(Calendar.DAY_OF_WEEK);
        System.out.println(year+" "+month+" "+day+" "+getweek(week));//2026 1 24 星期六
        getweek(week);

    }

    private static String getweek(int week) {
        String arr[] = {"","星期天","星期一","星期二","星期三","星期四","星期五","星期六"};
        return arr[week];
    }

}

2.1LocalDate （年月日）

public static void main(String[] args) {
    //当前时间的日历对象  包括年月日
    LocalDate localDate = LocalDate.now();
    System.out.println(localDate);
    //获得指定时间的日历对象
    LocalDate localDate1 = LocalDate.of(2024,4,2);
    System.out.println(localDate1);

    System.out.println("==========================");

    //get方法获取日历中每个属性的值
    //年
    int year   = localDate.getYear();
    System.out.println(year);//2026
    //月： 第一种形式
    int month = localDate.getMonthValue();
    System.out.println(month);//1
    // 第二种形式
    Month month1 = localDate.getMonth();
    System.out.println(month1.getValue());//1
    //日
    int day = localDate.getDayOfMonth();
    System.out.println(day);//23
    //周
    DayOfWeek dayOfWeek = localDate1.getDayOfWeek();
    System.out.println(dayOfWeek); //TUESDAY
    System.out.println(dayOfWeek.getValue());//2

    System.out.println("==========================");

    //is开头的方法表示判断
    boolean after = localDate.isAfter(localDate);
    System.out.println(after);//false
    boolean after1 = localDate1.isAfter(localDate);
    System.out.println(after1);//false

    System.out.println("==========================");

    //with开头的表示修改方法 只能修改年月日
    LocalDate localDate2 = localDate1.withYear(2000);
    System.out.println(localDate2);//2000-04-02

    System.out.println("==========================");

    //minus开头的方法表示减少，只能减少年月日
    LocalDate localDate3 = localDate.minusYears(1);
    System.out.println(localDate3);//2025-01-23
    //plus开头的方法表示增加，只能增加年月日
    LocalDate localDate4 = localDate.plusYears(1);
    System.out.println(localDate4);//2027-01-23

    System.out.println("==========================");

    //判断今天是不是你生日
    LocalDate bir = LocalDate.of(2026, 1, 12);
    Month today = Month.from(LocalDate.now());
    System.out.println("今天是你的生日吗"+today.equals(bir));

}

2.2LocalTime（时分秒）

public static void main(String[] args) {
    // 获取当前日历对象 包括时分秒
    LocalTime now = LocalTime.now();
    System.out.println("今天的时间"+now);

    int hour = now.getHour();//时
    System.out.println(hour);
    int minute = now.getMinute();//分
    System.out.println(minute);
    int second = now.getSecond();//秒
    System.out.println(second);
    int nano = now.getNano();//纳秒
    System.out.println(nano);

    System.out.println("==========================");
    System.out.println(LocalTime.of(11, 12));
    System.out.println(LocalTime.of(11, 12, 30));
    System.out.println(LocalTime.of(11, 12, 30,2000));
    LocalTime localTime = LocalTime.of(11, 12, 30,2000);

    System.out.println("==========================");
    //is系列的方法
    System.out.println(localTime.isBefore(now));//true
    System.out.println(localTime.isAfter(now));//false

    //with系列的方法 只能修改时分秒
    System.out.println( now.withHour(2));//02:31:08.892886700

    //minus系列的方法 只能减少时分秒
    System.out.println(now.minusHours(2));//15:31:08.892886700
    //plus系列的方法，只能增加时分秒
    System.out.println(now.plusHours(2));//19:31:08.892886700

2.3 localDateTime（年月日时分秒）

public static void main(String[] args) {
    //当前时间的日历对象 包括年月日时分秒
    LocalDateTime localDateTime = LocalDateTime.now();
    System.out.println("今天是"+localDateTime);//今天是2026-01-23T16:17:35.229178800
    System.out.println(localDateTime.getYear());//年 2026
    System.out.println(localDateTime.getMonthValue());//月 1
    System.out.println(localDateTime.getDayOfMonth());//日23
    System.out.println(localDateTime.getHour());//时 16

    System.out.println("==========================");

    //日：当年的第几天
    System.out.println(localDateTime.getDayOfYear());
    //月：
    Month month = localDateTime.getMonth();
    System.out.println(month.getValue());//1
    //星期：
    DayOfWeek dayOfWeek = localDateTime.getDayOfWeek();
    System.out.println(dayOfWeek.getValue());//5

    System.out.println("==========================");

    //转换为LocalData对象
    LocalDate ld = localDateTime.toLocalDate();
    System.out.println(ld);//2026-01-23
    //转换为LocalTime对象
    LocalTime lt = localDateTime.toLocalTime();
    System.out.println(lt);//16:36:03.871771300
    System.out.println(lt.getHour());//16
    System.out.println(lt.getMinute());//36
    System.out.println(lt.getSecond()); //3

3.日期格式化类

3.1 SimpleDateFormat

将日期对象解析为字符串

private static void method() {
    //使用空参构造创建对象，默认格式
    SimpleDateFormat sdf1 = new SimpleDateFormat();
    Date d1 = new Date(0l);
    System.out.println(sdf1.format(d1));//1970/1/1 08:00
    //使用带参构造创建对象
    SimpleDateFormat sdf2 = new SimpleDateFormat("yyyy年MM月dd日 HH:mm:ss");
    Date d2 = new Date(0l);
    System.out.println(sdf2.format(d2));//1970年01月01日 08:00:00
}

将字符串解析为日期对象

//1.定义一个字符串来表示时间
String sj = "2025-11-11  11:11:11";
//2.利用构造方法创建对象
// 细节：创建对象的格式要跟字符串的格式完全一致
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
Date d1 = sdf.parse(sj);
//3.打印结果
System.out.println(d1.getTime());

练习

public static void main(String[] args) throws ParseException {
    //肯德基举办活动 从10点到10点10  小明下单时间为10点10点01 小明是否参与活动
    String starttime = "10:00:00";
    String endtime = "10:10:00";
    String ordertime = "10:01:00";
    SimpleDateFormat sdf = new SimpleDateFormat("HH:mm:ss");
    Date start = sdf.parse(starttime);
    Date end = sdf.parse(endtime);
    Date order = sdf.parse(ordertime);
    if (order.getTime() <= end.getTime()&&order.getTime() >= start.getTime()) {
        System.out.println("参与了活动" );
    }else {
        System.out.println("没有参加活动");
    }
}

4.工具类

4.1Period(年月日)

public static void main(String[] args) {
    LocalDate now = LocalDate.now();
    System.out.println(now);//2026-01-24

    LocalDate birthday = LocalDate.of(2001,1,1);
    System.out.println(birthday);//2001-01-01

   Period period = Period.between(birthday,now);
    System.out.println("相差的时间间隔Period is " + period);//相差的时间间隔Period is P25Y23D
   System.out.println(period.getYears());//25
   System.out.println(period.getMonths());//0
   System.out.println(period.getDays());//23
    System.out.println(period.toTotalMonths());//300

4.2Duration（时分秒）

//用于计算两个时间间隔（秒，纳秒）
LocalTime time = LocalTime.now();
System.out.println(time);
LocalTime time1 = LocalTime.of(1,1,1);
System.out.println(time1);

Duration duration = Duration.between(time,time1);
System.out.println(duration);
System.out.println(duration.toDays());
System.out.println(duration.toHours());
System.out.println(duration.toMinutes());

4.3 ChronoUnit（年月日时分秒）

LocalDateTime time =  LocalDateTime.now();
System.out.println(time);

LocalDateTime bir = LocalDateTime.of(2001, 6, 17, 6, 20, 20);
System.out.println(bir);
System.out.println("相差的年数为"+ChronoUnit.YEARS.between(bir,time));
System.out.println("相差的月数为"+ChronoUnit.MONTHS.between(bir,time));
System.out.println("相差的天数为"+ChronoUnit.DAYS.between(bir,time));
System.out.println("相差的小时数为"+ChronoUnit.HOURS.between(bir,time));
System.out.println("相差的分钟数为"+ChronoUnit.MINUTES.between(bir,time));
System.out.println("相差的秒数为"+ChronoUnit.SECONDS.between(bir,time));
System.out.println("相差的毫秒数为"+ChronoUnit.MILLIS.between(bir,time));
System.out.println("相差的纳秒数为"+ChronoUnit.NANOS.between(bir,time));
System.out.println("相差的半天数为"+ChronoUnit.HALF_DAYS.between(bir,time));
System.out.println("相差的十年数为"+ChronoUnit.DECADES.between(bir,time));
System.out.println("相差的周数为"+ChronoUnit.WEEKS.between(bir,time));
System.out.println("相差的世纪（百年）数为"+ChronoUnit.CENTURIES.between(bir,time));
System.out.println("相差的千年数为"+ChronoUnit.MILLENNIA.between(bir,time));
System.out.println("相差的纪元数为"+ChronoUnit.ERAS.between(bir,time));