1.阅读

1.1Instant

①获取当前时间Instant.now(),得到一个时间戳
②当前的时间戳加上或减取某个Duration

1.2Duration

可以计算两个时间间的差值，计算的结果是 秒+纳秒，分两个字段存储
因此纳秒存储的是说，相差了n秒零纳秒，所以int就可以存储纳秒

1.3Period

可以设置两日期的时间差

1.4ZonedTime ZonedDateTime

1.5LocalTime

1.6LocalDate

1.7LocalDateTime

本来是想整理好的，可是Java核心卷的东西实在看的头疼。我感觉在开发中用到最多的就是
LocalXXX 和 Instant /Period 和 Duration

2.场景练习

2.1Date和Instant和LocalDateTime的转换

Date—-> Instant

Instant instant = Instant.ofEpochMilli(date.getTime());

Instant—>Date

Date date1 = new Date(Instant.now().toEpochMilli());
Date date2 =Date.from(instant)

Date—>LocalDateTime(Date -> Instant -> ZoneDateTime)

LocalDateTime localDateTime1 = Instant.ofEpochMilli(date2.getTime()).atZone(ZoneId.systemDefault()).toLocalDateTime();

LocalDateTime —>Date( LocalDateTime—> ZoneDatetime—> Instant—>Date)

Instant instant1 = now.atZone(ZoneId.systemDefault()).toInstant();
Date from1 = Date.from(instant1);

2.2常用操作

①LocalDateTime获取指定日期 00:00:00 和 23：59：59

    @Test
    public void testGetMaxAndMin()
    {
        LocalDateTime localDateTime = LocalDateTime.now();
        LocalDateTime minTime = LocalDateTime.of(localDateTime.toLocalDate(), LocalTime.MIN);
        System.out.println(minTime);
        LocalDateTime maxTime = LocalDateTime.of(localDateTime.toLocalDate(), LocalTime.MAX);
        System.out.println(maxTime);
    }

②计算A和B的LocalDateTime的相差天数（精确到秒）

    @Test
    public void testBetween() {
        LocalDateTime now = LocalDateTime.now();
        System.out.println(now);
        LocalDateTime localDateTime = now.plusDays(20);
        System.out.println(localDateTime);
        Duration between = Duration.between(now, localDateTime);
        long l = between.toDays();
        System.out.println(l);
    }