Java8学习笔记 — 新日期时间API

LocalDate、LocalTime、LocalDateTime类的实例是不可变的对象，分别表示使用ISO8601日历系统的日期、时间、日期和时间。它们提供了简单的日期或时间，并不包含当前的时间信息，也不包含与时区相关的信息。

@Test
public void test1() {
	LocalDateTime ldt = LocalDateTime.now();
	System.out.println(ldt);

	LocalDateTime ldt2 = LocalDateTime.of(2017, 05, 24, 14, 18, 30);
	System.out.println(ldt2);

	System.out.println(ldt.plusYears(2));
	System.out.println(ldt.minusYears(2));
	System.out.println(ldt.getYear());
	System.out.println(ldt.getMonth());
	System.out.println(ldt.getDayOfMonth());
	System.out.println(ldt.getDayOfYear());
	System.out.println(ldt.getMinute());
}

Instant：时间戳（以Unix元年：1970年1月1日00:00:00到某个时间之间的毫秒值）

@Test
public void test2() {
	Instant ins1 = Instant.now(); // 默认获取UTC时区
	System.out.println(ins1);

	OffsetDateTime odt = ins1.atOffset(ZoneOffset.ofHours(8));
	System.out.println(odt);

	System.out.println(ins1.toEpochMilli());

	Instant ins2 = Instant.ofEpochMilli(1000);
	System.out.println(ins2);
}

Duration和Period：计算两个时间间隔

@Test
public void test4() {
	LocalDate ld1 = LocalDate.of(2016, 10, 10);
	LocalDate ld2 = LocalDate.now();
	Period period = Period.between(ld1, ld2);
	System.out.println(period);
	System.out.println(period.getYears());
	System.out.println(period.getMonths());
	System.out.println(period.getDays());
}

@Test
public void test3() {
	Instant ins1 = Instant.now();
	try {
		Thread.sleep(1000);
	} catch (InterruptedException e) {
		e.printStackTrace();
	}
	Instant ins2 = Instant.now();
	Duration duration = Duration.between(ins1, ins2);
	System.out.println(duration.toMillis());

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

	LocalTime lt1 = LocalTime.now();
	try {
		Thread.sleep(1000);
	} catch (InterruptedException e) {
		e.printStackTrace();
	}
	LocalTime lt2 = LocalTime.now();
	System.out.println(Duration.between(lt1, lt2).toMillis());
}

TemporalAdjuster：时间校正器

TemporalAdjusters：该类通过静态方法提供了大量的常用TemporalAdjuster的实现

@Test
public void test5() {
	LocalDateTime ldt = LocalDateTime.now();
	System.out.println(ldt);

	LocalDateTime ldt2 = ldt.withDayOfMonth(18);
	System.out.println(ldt2);

	LocalDateTime ldt3 = ldt.with(TemporalAdjusters.firstDayOfMonth());
	System.out.println(ldt3);

	LocalDateTime ldt4 = ldt.with(TemporalAdjusters.firstDayOfNextYear());
	System.out.println(ldt4);

	System.out.println("---------------------");
	System.out.println(ldt.withMonth(3));
	System.out.println(ldt.withMinute(12));
	System.out.println(ldt.withHour(5));
	System.out.println("---------------------");
	System.out.println(ldt.with(TemporalAdjusters.lastDayOfMonth()));
	System.out.println(ldt.with(TemporalAdjusters.lastDayOfYear()));
	System.out.println(ldt.with(TemporalAdjusters.next(DayOfWeek.MONDAY)));
	System.out.println(ldt.with(TemporalAdjusters.nextOrSame(DayOfWeek.MONDAY)));
}

DateTimeFormatter：日期时间格式化

@Test
public void test6() {
	DateTimeFormatter dtf = DateTimeFormatter.ISO_DATE;
	LocalDateTime ldt = LocalDateTime.now();
	String str = ldt.format(dtf);
	System.out.println(str);

	DateTimeFormatter dtf2 = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
	String str2 = ldt.format(dtf2);
	System.out.println(str2);

	LocalDateTime newDate = ldt.parse(str2, dtf2);
	System.out.println(newDate);
}

ZoneTime、ZoneDate、ZoneDateTime：时区处理

每个时区都对应着ID，地区ID都为“{区域}/{城市}”的格式，例如：Aisa/Shanghai

ZoneId：该类中包含了所有的时区信息

         getAvailableZoneIds()：可以获取所有时区信息

         of(String id)：用指定的时区信息获取ZoneId对象

@Test
public void test8() {
	LocalDateTime ldt = LocalDateTime.now(ZoneId.of("Pacific/Majuro"));
	System.out.println(ldt);

	LocalDateTime ldt2 = LocalDateTime.now(Clock.systemDefaultZone());
	System.out.println(ldt2);

	LocalDateTime ldt3 = LocalDateTime.now(ZoneId.of("America/Los_Angeles"));
	ZonedDateTime zdt = ldt3.atZone(ZoneId.of("Asia/Shanghai"));
	System.out.println(zdt);
}

@Test
public void test7() {
	Set<String> zoneIds = ZoneId.getAvailableZoneIds();
	zoneIds.forEach(System.out::println);
}