jdk1.8_时间类

技术
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java.time

LocalDate(年月日)

本地日期和时间

1. 最值

最大支持 +999999999-12-31 最小支持-999999999-01-01

2. 比较方法

equals 

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LocalDate today = LocalDate.now();
LocalDate tomorrow = today.plus(1, ChronoUnit.DAYS);
LocalDate yesterday = tomorrow.minusDays(2);
if(today.equals(tomorrow.minusDays(1))) {
    System.out.println("true");
}else {
    System.out.println("false");
}

3. now()方法

获取当前时间，无参时为当前系统默认时区，参数为时区id 

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/**
 * Obtains the current date from the system clock in the specified time-zone.
 * <p>
 * This will query the {@link Clock#system(ZoneId) system clock} to obtain the current date.
 * Specifying the time-zone avoids dependence on the default time-zone.
 * <p>
 * Using this method will prevent the ability to use an alternate clock for testing
 * because the clock is hard-coded.
 *
 * @param zone  the zone ID to use, not null
 * @return the current date using the system clock, not null
 */
public static LocalDate now(ZoneId zone) {
    return now(Clock.system(zone));
}
/**
 * Obtains the current date from the system clock in the default time-zone.
 * <p>
 * This will query the {@link Clock#systemDefaultZone() system clock} in the default
 * time-zone to obtain the current date.
 * <p>
 * Using this method will prevent the ability to use an alternate clock for testing
 * because the clock is hard-coded.
 *
 * @return the current date using the system clock and default time-zone, not null
 */
public static LocalDate now() {
    return now(Clock.systemDefaultZone()); 
}

4. plus()方法

public LocalDate plus(long amountToAdd, TemporalUnit unit) amountToAdd 要增加的总数 ；unit 时间单位 详见 ChronoUnit(TemporalUnit的实现类)

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LocalDate today = LocalDate.now();
LocalDate tomorrow = today.plus(1, ChronoUnit.DAYS);

//plusYears(long yearsToAdd)\plusMonths(long monthsToAdd)\plusWeeks(long weeksToAdd)\plusDays(long daysToAdd)

5. minus()方法

public LocalDate minus(long amountToSubtract, TemporalUnit unit)

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LocalDate today = LocalDate.now();
LocalDate tomorrow = today.minus(1, ChronoUnit.DAYS);

//minusYears(long yearsToSubtract)\minusMonths(long monthsToSubtract)\minusWeeks(long weeksToSubtract)\minusDays(long daysToSubtract)

6. of()方法、getDayOfWeek()方法

LocalDate of(int year, Month month, int dayOfMonth)/LocalDate of(int year, int month, int dayOfMonth)
LocalDate.getDayOfWeek() 判断传入日期是一周中的第几天 return DayOfWeek对象

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LocalDate independenceDay = LocalDate.of(2014, Month.JULY, 4);
DayOfWeek dayOfWeek = independenceDay.getDayOfWeek();
System.out.println(dayOfWeek);//FRIDAY
System.out.println(dayOfWeek.getValue());//5

7. DateTimeFormatter

格式化时间，线程安全，类内创建一次可复用

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//实例化 不指定时区
DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm");
//实例化 指定时区
DateTimeFormatter formatter = DateTimeFormatter.ofPattern("E, yyyy-MMMM-dd HH:mm", Locale.US);

ZonedDateTime zdt = ZonedDateTime.now();
DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd'T'HH:mm ZZZZ");
System.out.println(formatter.format(zdt));//2020-09-28T11:55 GMT+08:00

DateTimeFormatter zhFormatter = DateTimeFormatter.ofPattern("yyyy MMM dd EE HH:mm", Locale.CHINA);
System.out.println(zhFormatter.format(zdt));//2020 九月 28 星期一 11:55

DateTimeFormatter usFormatter = DateTimeFormatter.ofPattern("E, MMMM/dd/yyyy HH:mm", Locale.US);
System.out.println(usFormatter.format(zdt));//Mon, September/28/2020 11:55

System.out.println(DateTimeFormatter.ISO_DATE_TIME.format(zdt));//2020-09-28T11:55:39.209+08:00[Asia/Shanghai]

保留字母定义

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* All letters 'A' to 'Z' and 'a' to 'z' are reserved as pattern letters. The
* following pattern letters are defined:
* <pre>
*  Symbol  Meaning                     Presentation      Examples
*  ------  -------                     ------------      -------
*   G       era                         text              AD; Anno Domini; A
*   u       year                        year              2004; 04
*   y       year-of-era                 year              2004; 04
*   D       day-of-year                 number            189
*   M/L     month-of-year               number/text       7; 07; Jul; July; J
*   d       day-of-month                number            10
*
*   Q/q     quarter-of-year             number/text       3; 03; Q3; 3rd quarter
*   Y       week-based-year             year              1996; 96
*   w       week-of-week-based-year     number            27
*   W       week-of-month               number            4
*   E       day-of-week                 text              Tue; Tuesday; T
*   e/c     localized day-of-week       number/text       2; 02; Tue; Tuesday; T
*   F       week-of-month               number            3
*
*   a       am-pm-of-day                text              PM
*   h       clock-hour-of-am-pm (1-12)  number            12
*   K       hour-of-am-pm (0-11)        number            0
*   k       clock-hour-of-am-pm (1-24)  number            0
*
*   H       hour-of-day (0-23)          number            0
*   m       minute-of-hour              number            30
*   s       second-of-minute            number            55
*   S       fraction-of-second          fraction          978
*   A       milli-of-day                number            1234
*   n       nano-of-second              number            987654321
*   N       nano-of-day                 number            1234000000
*
*   V       time-zone ID                zone-id           America/Los_Angeles; Z; -08:30
*   z       time-zone name              zone-name         Pacific Standard Time; PST
*   O       localized zone-offset       offset-O          GMT+8; GMT+08:00; UTC-08:00;
*   X       zone-offset 'Z' for zero    offset-X          Z; -08; -0830; -08:30; -083015; -08:30:15;
*   x       zone-offset                 offset-x          +0000; -08; -0830; -08:30; -083015; -08:30:15;
*   Z       zone-offset                 offset-Z          +0000; -0800; -08:00;
*
*   p       pad next                    pad modifier      1
*
*   '       escape for text             delimiter
*   ''      single quote                literal           '
*   [       optional section start
*   ]       optional section end
*   #       reserved for future use
*   {       reserved for future use
*   }       reserved for future use

LocalDateTime(年月日时分秒)

本地日期和时间

1. 常用方法案例

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LocalDateTime ldt = LocalDateTime.of(2014, Month.DECEMBER, 31, 23, 59, 59);

DayOfWeek dayOfWeek = ldt.getDayOfWeek();
System.out.println(dayOfWeek);      // WEDNESDAY

Month month = ldt.getMonth();
System.out.println(month);          // DECEMBER

long minuteOfDay = ldt.getLong(ChronoField.MINUTE_OF_DAY);
System.out.println(minuteOfDay);    // 23*60+59=1439

long dayOfWeekLong = ldt.getLong(ChronoField.DAY_OF_WEEK);
System.out.println(dayOfWeekLong);    // 3

DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");

LocalDateTime parsed = LocalDateTime.parse("2016-12-01 23:59:59", formatter);
String string = parsed.format(formatter);
System.out.println(string);     // 2016-12-01 23:59:59

2. Instant时间戳

在java.util.Date类与LocalDate、LocalDateTime类之间转换中 均可以通过Instant作为中间类完成转换

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LocalDateTime ldt = LocalDateTime.of(2014, Month.DECEMBER, 31, 23, 59, 59);
//获取当前默认时区下ldt转换成的时间戳
      Instant instant = ldt.atZone(ZoneId.systemDefault()).toInstant();

      Date legacyDate = Date.from(instant);
      System.out.println(legacyDate);     // Wed Dec 31 23:59:59 CET 2014

LocalTime(时分秒)

本地日期和时间

1. Clock

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Clock clock = Clock.systemDefaultZone();
//返回1970-01-01T00:00Z (UTC)至今的毫秒数，即按毫秒单位的unix时间戳
long t0 = clock.millis();
System.out.println(t0);

Instant instant = clock.instant();
Date legacyDate = Date.from(instant);
System.out.println(legacyDate);

2. ZoneId.getRules(),isBefore()

getRules 当前默认时区与指定时区间的转换公式
isBefore 当前时间是否在指定时间之前
ChronoUnit.between 按指定时间单位计算俩时间的差

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ZoneId zone1 = ZoneId.of("Europe/Berlin");
ZoneId zone2 = ZoneId.of("Brazil/East");

System.out.println(zone1.getRules());//ZoneRules[currentStandardOffset=+01:00]
System.out.println(zone2.getRules());//ZoneRules[currentStandardOffset=-03:00]

// time
LocalTime now1 = LocalTime.now(zone1);//10:17:39.043
LocalTime now2 = LocalTime.now(zone2);//05:17:39.050

System.out.println(now1);
System.out.println(now2);

System.out.println(now1.isBefore(now2));  // false

long hoursBetween = ChronoUnit.HOURS.between(now1, now2);
long minutesBetween = ChronoUnit.MINUTES.between(now1, now2);
System.out.println(hoursBetween);//-4
System.out.println(minutesBetween);//-299


// create time

LocalTime now = LocalTime.now();
System.out.println(now);//16:17:39.052

LocalTime late = LocalTime.of(23, 59, 59);
System.out.println(late);//23:59:59
DateTimeFormatter germanFormatter =
                DateTimeFormatter
                        .ofLocalizedTime(FormatStyle.SHORT)
                        .withLocale(Locale.GERMAN);

LocalTime formateTime = LocalTime.parse("13:37", germanFormatter);
System.out.println(formateTime);//13:37

ZonedDateTime

带时区的日期和时间(ISO-8601)

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ZonedDateTime  zonedDateTime = ZonedDateTime.now();
System.out.println(zonedDateTime);//2020-09-28T17:19:44.836+08:00[Asia/Shanghai]
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