2021-04-02新的时间类的使用

package text2;

import java.time.*;
import java.time.format.DateTimeFormatter;
import java.time.temporal.TemporalAdjusters;

public class DateUtil {
    public static void main(String[] args) {
        LocalDate d = LocalDate.now(); // 当前日期
        LocalTime t = LocalTime.now(); // 当前时间
        LocalDateTime dt = LocalDateTime.now(); // 当前日期和时间
        LocalDate localDate = dt.toLocalDate();
        LocalTime localTime = dt.toLocalTime();
        System.out.println(localDate);
        System.out.println(localTime);
        System.out.println(d); // 严格按照ISO 8601格式打印
        System.out.println(t); // 严格按照ISO 8601格式打印
        System.out.println(dt); // 严格按照ISO 8601格式打印
        // 指定日期和时间:
        LocalDate d2 = LocalDate.of(2019, 11, 30); // 2019-11-30, 注意11=11月
        LocalTime t2 = LocalTime.of(15, 16, 17); // 15:16:17
        LocalDateTime dt2 = LocalDateTime.of(2019, 11, 30, 15, 16, 17);
        LocalDateTime dt3 = LocalDateTime.of(d2, t2);
        System.out.println(d2);
        System.out.println(t2);
        System.out.println(dt2);
        System.out.println(dt3);

        LocalDateTime dt4 = LocalDateTime.parse("2019-11-19T15:16:17");
        LocalDate d5 = LocalDate.parse("2019-11-19");
        LocalTime t6 = LocalTime.parse("15:16:17");
        System.out.println(dt4);
        System.out.println(d5);
        System.out.println(t6);
        /*  日期：yyyy-MM-dd
            时间：HH:mm:ss
            带毫秒的时间：HH:mm:ss.SSS
            日期和时间：yyyy-MM-dd'T'HH:mm:ss
            带毫秒的日期和时间：yyyy-MM-dd'T'HH:mm:ss.SSS
         */
        DateTimeFormatter dtf = DateTimeFormatter.ofPattern("yyyy/MM/dd HH:mm:ss");
        System.out.println(dtf.format(LocalDateTime.now()));

        // 用自定义格式解析:
        LocalDateTime dt7 = LocalDateTime.parse("2019/11/30 15:16:17", dtf);
        System.out.println(dt7);
        LocalDateTime ldt =LocalDateTime.of(2019,12,31,20,30,59);
        System.out.println(ldt);
        //加五天减三小时
        LocalDateTime ldt2= ldt.plusDays(5).minusHours(3);
        System.out.println(ldt2);
        //减一个月
        LocalDateTime ldt3= ldt.minusMonths(1).plusMonths(5);
        System.out.println(ldt3);


        LocalDateTime ldt4 = LocalDateTime.of(2019, 10, 26, 20, 30, 59);
        System.out.println(ldt4);
        // 日期变为31日:
        LocalDateTime ldt5 = ldt4.withDayOfMonth(31);
        System.out.println(ldt5); // 2019-10-31T20:30:59
        // 月份变为9:
        LocalDateTime ldt6 = ldt5.withMonth(9);
        System.out.println(ldt6); // 2019-09-30T20:30:59

        // 本月第一天0:00时刻:
        LocalDateTime firstDay = LocalDate.now().withDayOfMonth(1).atStartOfDay();
        System.out.println(firstDay);

        // 本月最后1天:
        LocalDate lastDay = LocalDate.now().with(TemporalAdjusters.lastDayOfMonth());
        System.out.println(lastDay);

        // 下月第1天:
        LocalDate nextMonthFirstDay = LocalDate.now().with(TemporalAdjusters.firstDayOfNextMonth());
        System.out.println(nextMonthFirstDay);

        // 本月第1个周一:
        LocalDate firstWeekday = LocalDate.now().with(TemporalAdjusters.firstInMonth(DayOfWeek.MONDAY));
        System.out.println(firstWeekday);
        System.out.println("==================================================");
//        要判断两个LocalDateTime的先后，可以使用isBefore()、isAfter()方法，对于LocalDate和LocalTime类似：
        LocalDateTime now = LocalDateTime.now();
        LocalDateTime target = LocalDateTime.of(2020, 11, 19, 8, 15, 0);
        System.out.println(now.isBefore(target));
        System.out.println(LocalDate.now().isBefore(LocalDate.of(2020, 11, 19)));
        System.out.println(LocalTime.now().isAfter(LocalTime.parse("08:15:00")));

        LocalDateTime start = LocalDateTime.of(2019, 11, 19, 8, 15, 0);
        LocalDateTime end = LocalDateTime.of(2020, 1, 9, 19, 25, 30);
        Duration d1 = Duration.between(start, end);
        System.out.println(d1); // PT1235H10M30S

        Period p = LocalDate.of(2019, 11, 19).until(LocalDate.of(2020, 1, 9));
        System.out.println(p); // P1M21D

        Duration d3 = Duration.ofHours(10); // 10 hours
        Duration d4 = Duration.parse("P1DT2H3M"); // 1 day, 2 hours, 3 minutes
        System.out.println(d3);
        System.out.println(d4);
    }
}

package text2;

import java.time.LocalDateTime;
import java.time.ZoneId;
import java.time.ZonedDateTime;

public class ZonedDateUtil {
    public static void main(String[] args) {
        ZonedDateTime zbj = ZonedDateTime.now(); // 默认时区
        ZonedDateTime zny = ZonedDateTime.now(ZoneId.of("America/New_York")); // 用指定时区获取当前时间
        System.out.println(zbj);
        System.out.println(zny);

        LocalDateTime ldt = LocalDateTime.of(2019, 9, 15, 15, 16, 17);
        ZonedDateTime zbj1 = ldt.atZone(ZoneId.systemDefault());
        ZonedDateTime zny1 = ldt.atZone(ZoneId.of("America/New_York"));
        System.out.println(zbj1);
        System.out.println(zny1);

        // 以中国时区获取当前时间:
        ZonedDateTime zbj2 = ZonedDateTime.now(ZoneId.of("Asia/Shanghai"));
        // 转换为纽约时间:
        ZonedDateTime zny2 = zbj2.withZoneSameInstant(ZoneId.of("America/New_York"));
        System.out.println(zbj2);
        System.out.println(zny2);
        LocalDateTime ldt3 = zbj2.toLocalDateTime();
        System.out.println(ldt3);
    }
}