java新時間類

時間

java8以前使用的時間很多方法都已經廢棄了，而且不是線程安全的，java8提供了一系列的時間類，這些時間類都是線程安全的

LocalDate、LocalTime、LocalDateTime

這三個關於時間的類在使用上都類似

/**
	 * LocalDate
	 */
@Test
public void test1() {
  LocalDate date1 = LocalDate.now();
  System.out.println(date1);//2020-03-30

  LocalDate plusYears = date1.plusYears(1);
  System.out.println(plusYears);//2021-03-30

  LocalDate minusDays = date1.minusDays(2);
  System.out.println(minusDays);//2020-03-28

  LocalDate date2 = LocalDate.of(2019, 3, 30);
  System.out.println(date2.getYear());//2019
}

/**
	 * LocalTime
	 */
@Test
public void test2() {
  LocalTime now = LocalTime.now();
  System.out.println(now);//21:15:23.418

  int minute = now.getMinute();
  System.out.println(minute);//15

  int second = now.getSecond();
  System.out.println(second);//23

  LocalTime of = LocalTime.of(10, 10, 10);
  System.out.println(of);//10:10:10

  LocalTime minusMinutes = of.minusMinutes(2);
  System.out.println(minusMinutes);//10:08:10

  LocalTime plusHours = of.plusHours(2);
  System.out.println(plusHours);//12:10:10
}

/**
	 * LocalDateTime
	 */
@Test
public void test3() {
  LocalDateTime now = LocalDateTime.now();
  System.out.println(now);//2020-03-30T21:20:37.961

  int minute = now.getMinute();
  System.out.println(minute);//20

  LocalDateTime plusMinutes = now.plusMinutes(20);
  System.out.println(plusMinutes);//2020-03-30T21:40:37.961

  LocalDateTime minusYears = now.minusYears(2);
  System.out.println(minusYears);//2018-03-30T21:20:37.961

  LocalDateTime of = LocalDateTime.of(2021, 3, 30, 21, 19, 50);
  System.out.println(of);//2021-03-30T21:19:50
}

時間戳

/**
	 * Instant
	 */
@Test
public void test4() {
  Instant now = Instant.now();
  System.out.println(now);//2020-03-30T13:26:10.640Z

  Instant plusSeconds = now.plusSeconds(10);
  System.out.println(plusSeconds);//2020-03-30T13:26:20.640Z

  //獲取時間戳相對於1970年0時0分0秒的毫秒數
  long epochMilli = plusSeconds.toEpochMilli();
  System.out.println(epochMilli);//1585574780640
}

Duration獲取時間間隔

/**
	 * Duration
	 */
@Test
public void test5() {
  Instant start = Instant.now();
  Instant end = start.plusSeconds(10);
  Duration duration = Duration.between(start, end);
  long seconds = duration.getSeconds();
  //獲取時間間隔的秒數
  System.out.println(seconds);//10

  //獲取時間間隔的毫秒數
  long millis = duration.toMillis();
  System.out.println(millis);//10000
}

Peroid獲取日期間隔

@Test
public void test6() {
  LocalDate date1 = LocalDate.now();
  LocalDate date2 = date1.plusYears(2);
  Period period = Period.between(date1, date2);
  //獲取兩時間間隔的月數,指兩個月份的間隔數，並不是時間間隔的總月數
  int months = period.getMonths();
  System.out.println(months);//0
}

TemporalAdjuster矯正日期

@Test
public void test7() {
  LocalDate date1 = LocalDate.now();
  System.out.println(date1);//2020-03-31

  //TemporalAdjusters類中封裝了一些常用地時間矯正方法
  TemporalAdjuster next = TemporalAdjusters.next(DayOfWeek.FRIDAY);
  LocalDate date2 = date1.with(next);
  System.out.println(date2);//2020-04-03

  //自定義時間矯正器
  LocalDate date3 = date1.with(x->{
    LocalDate ld=(LocalDate)x;
    DayOfWeek dayOfWeek = ld.getDayOfWeek();
    if(dayOfWeek.equals(DayOfWeek.FRIDAY)) {
      return ld.plusDays(3);
    }else if(dayOfWeek.equals(DayOfWeek.SATURDAY)) {
      return ld.plusDays(2);
    }else {
      return ld.plusDays(1);
    }
  });
  System.out.println(date3);//2020-04-01
}

由於TemporalAdjuster是一個函數式介面，所以我們可以使用lambda表達式自定義矯正規則

@FunctionalInterface
public interface TemporalAdjuster {
  Temporal adjustInto(Temporal temporal);
}

DateTimeFormatter格式化日期時間

@Test
public void test8() {
  LocalDateTime dateTime1 = LocalDateTime.now();
  System.out.println(dateTime1);//2020-03-31T18:28:04.256

  DateTimeFormatter formatter1 = DateTimeFormatter.ISO_DATE;
  String format1 = dateTime1.format(formatter1);
  System.out.println(format1);//2020-03-31

  DateTimeFormatter formatter2 = DateTimeFormatter.ofPattern("yyyy年MM月dd日HH時mm分ss秒");
  String format2 = dateTime1.format(formatter2);
  System.out.println(format2);//2020年03月31日18時28分04秒

  LocalDateTime dateTime2 = LocalDateTime.parse(format2, formatter2);
  System.out.println(dateTime2);//2020-03-31T18:28:04
}

ZoneDate

@Test
public void test9() {
  //獲取可用時區
  ZoneId.getAvailableZoneIds().forEach(System.out::println);

  LocalDate date1 = LocalDate.now(ZoneId.of("Asia/Tokyo"));
  System.out.println(date1);//2020-03-31
}

ZoneTime

@Test
public void test10() {
  LocalTime time1 = LocalTime.now(ZoneId.of("Asia/Tokyo"));
  System.out.println(time1);//19:44:15.228

  OffsetTime atOffset = time1.atOffset(ZoneOffset.ofHours(2));
  System.out.println(atOffset);//19:44:15.228+02:00
}

ZoneDateTime

@Test
public void test11() {
  LocalDateTime dateTime1 = LocalDateTime.now(ZoneId.of("Asia/Shanghai"));
  System.out.println(dateTime1);//2020-03-31T18:51:07.136

  ZonedDateTime atZone = dateTime1.atZone(ZoneId.of("Asia/Shanghai"));
  System.out.println(atZone);//2020-03-31T18:51:07.136+08:00[Asia/Shanghai]	+09:00表示時間比格林尼治時間快9小時
}