JDK1.8新特性 日期的使用（四）

新的日期API LocalDate | LocalTime | LocalDateTime

public class Main {

    /**
     * 关于LocalDateTime
     */
    @Test
    public void test1(){
        LocalDateTime date=LocalDateTime.now();
        System.out.println(date);//输出：2019-03-24T10:20:21.656

        System.out.println(date.getYear());
        System.out.println(date.getMonthValue());
        System.out.println(date.getDayOfMonth());
        System.out.println(date.getHour());
        System.out.println(date.getMinute());
        System.out.println(date.getSecond());
        System.out.println(date.getNano());

        // 手动创建一个LocalDateTime实例
        LocalDateTime date2 = LocalDateTime.of(2017, 12, 17, 9, 31, 31, 31);
        System.out.println(date2);
        // 进行加操作，得到新的日期实例
        LocalDateTime date3 = date2.plusDays(12);
        System.out.println(date3);
        // 进行减操作，得到新的日期实例
        LocalDateTime date4 = date3.minusYears(2);
        System.out.println(date4);
    }

    /**
     * 关于时间戳
     */
    @Test
    public void test2(){
        Instant ins=Instant.now();
        //默认获取UTC时区
        System.out.println(ins);
        System.out.println(LocalDateTime.now().toInstant(ZoneOffset.of("+8")).toEpochMilli());
        System.out.println(System.currentTimeMillis());

        System.out.println(Instant.now().toEpochMilli());
        System.out.println(Instant.now().atOffset(ZoneOffset.ofHours(8)).toInstant().toEpochMilli());

    }

    /**
     *
     */
    @Test
    public void test3(){
        // Duration:计算两个时间之间的间隔
        // Period：计算两个日期之间的间隔
        Instant ins1 = Instant.now();
        try {
            Thread.sleep(1000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        Instant ins2 = Instant.now();
        Duration dura = Duration.between(ins1, ins2);
        System.out.println(dura.getSeconds());
        System.out.println(dura.toMillis());

       System.out.println("======================");
        LocalTime localTime = LocalTime.now();
        try {
            Thread.sleep(1000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        LocalTime localTime2 = LocalTime.now();
        Duration du2 = Duration.between(localTime, localTime2);
        System.out.println(du2);
        System.out.println(du2.toMillis());
    }
    @Test
    public void test4(){
        LocalDate localDate =LocalDate.now();
        try {
            Thread.sleep(1000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        LocalDate localDate2 = LocalDate.of(2019,3,25);
        Period pe = Period.between(localDate, localDate2);
        System.out.println(pe.getDays());
    }
    @Test
    public void test5(){
        // temperalAdjust 时间校验器
        // 例如获取下周日  下一个工作日
        LocalDateTime ldt1 = LocalDateTime.now();
        System.out.println(ldt1);

        // 获取一年中的第一天
        LocalDateTime ldt2 = ldt1.withDayOfYear(1);
        System.out.println(ldt2);
        // 获取一个月中的第一天
        LocalDateTime ldt3 = ldt1.withDayOfMonth(1);
        System.out.println(ldt3);

        LocalDateTime ldt4 = ldt1.with(TemporalAdjusters.next(DayOfWeek.FRIDAY));
        System.out.println(ldt4);

        // 获取下一个工作日
        LocalDateTime ldt5 = ldt1.with((t) -> {
            LocalDateTime ldt6 = (LocalDateTime)t;
            DayOfWeek dayOfWeek = ldt6.getDayOfWeek();
            if (DayOfWeek.FRIDAY.equals(dayOfWeek)){
                return ldt6.plusDays(3);
            }
            else if (DayOfWeek.SATURDAY.equals(dayOfWeek)){
                return ldt6.plusDays(2);
            }
            else {
                return ldt6.plusDays(1);
            }
        });
        System.out.println(ldt5);
    }
    @Test
    public void test6(){
        // DateTimeFormatter: 格式化时间/日期
        // 自定义格式
        LocalDateTime ldt = LocalDateTime.now();
        DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy年MM月dd日");
        String strDate1 = ldt.format(formatter);
        String strDate = formatter.format(ldt);
        System.out.println(strDate);
        System.out.println(strDate1);

        // 使用api提供的格式
        DateTimeFormatter dtf = DateTimeFormatter.ISO_DATE;
        LocalDateTime ldt2 = LocalDateTime.now();
        String strDate3 = dtf.format(ldt2);
        System.out.println(strDate3);

        // 解析字符串to时间
        DateTimeFormatter df = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
        LocalDateTime time = LocalDateTime.now();
        String localTime = df.format(time);
        LocalDateTime ldt4 = LocalDateTime.parse("2017-09-28 17:07:05",df);
        System.out.println("LocalDateTime转成String类型的时间："+localTime);
        System.out.println("String类型的时间转成LocalDateTime："+ldt4);
    }
    @Test
    public void test7(){
        LocalDateTime now = LocalDateTime.now(ZoneId.of("Asia/Shanghai"));
        System.out.println(now);

        LocalDateTime now2 = LocalDateTime.now();
        ZonedDateTime zdt = now2.atZone(ZoneId.of("Asia/Shanghai"));
        System.out.println(zdt);

        Set set = ZoneId.getAvailableZoneIds();
        set.stream().forEach(System.out::println);
    }
}

1、LocalDate

@Test
public void test1(){
    //获取当前日期,只含年月日 固定格式 yyyy-MM-dd    2018-05-04
    LocalDate today = LocalDate.now();

    // 根据年月日取日期，5月就是5，
    LocalDate oldDate = LocalDate.of(2018, 5, 1);

    // 根据字符串取：默认格式yyyy-MM-dd，02不能写成2
    LocalDate yesteday = LocalDate.parse("2018-05-03");

    // 如果不是闰年 传入29号也会报错
    LocalDate.parse("2018-02-29");

}
@Test
public void test2(){

    //2018-05-04
    LocalDate today = LocalDate.now();
    // 取本月第1天： 2018-05-01
    LocalDate firstDayOfThisMonth = today.with(TemporalAdjusters.firstDayOfMonth());
    // 取本月第2天：2018-05-02
    LocalDate secondDayOfThisMonth = today.withDayOfMonth(2);
    // 取本月最后一天，再也不用计算是28，29，30还是31： 2018-05-31
    LocalDate lastDayOfThisMonth = today.with(TemporalAdjusters.lastDayOfMonth());
    // 取下一天：2018-06-01
    LocalDate firstDayOf2015 = lastDayOfThisMonth.plusDays(1);
    // 取2018年10月第一个周三 so easy?：  2018-10-03
    LocalDate thirdMondayOf2018 = LocalDate.parse("2018-10-01").with(TemporalAdjusters.firstInMonth(DayOfWeek.WEDNESDAY));
}

2、LocalDateTime

    @Test
    public void test1(){
        //转化为时间戳  毫秒值
        long time1 = LocalDateTime.now().toInstant(ZoneOffset.of("+8")).toEpochMilli();
        long time2 = System.currentTimeMillis();
        //时间戳转化为localdatetime
        DateTimeFormatter df= DateTimeFormatter.ofPattern("YYYY-MM-dd HH:mm:ss.SSS");
        System.out.println(df.format(LocalDateTime.ofInstant(Instant.ofEpochMilli(time1), ZoneId.of("Asia/Shanghai"))));
    }

3、LocalTime

    @Test
    public void test1(){
        //16:25:46.448(纳秒值)
        LocalTime todayTimeWithMillisTime = LocalTime.now();
        //16:28:48 不带纳秒值
        LocalTime todayTimeWithNoMillisTime = LocalTime.now().withNano(0);
        LocalTime time1 = LocalTime.parse("23:59:59");
    }