文章目录：
7.TestTemporalAdjuster、TestTemporalAdjusters
1.新旧对比（线程安全问题）
我们先来看下面的代码：👇👇👇（关于代码中某些类中的某些方法，我在这里就不说了，大家可以去查找api文档）
package com.szh.java8.datetime; import java.text.SimpleDateFormat; import java.time.LocalDate; import java.time.format.DateTimeFormatter; import java.util.ArrayList; import java.util.Date; import java.util.List; import java.util.concurrent.*; /** * */ public class TestSimpleDateFormat { public static void main(String[] args) throws ExecutionException, InterruptedException { SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMdd"); Callable<Date> task1 = new Callable<Date>() { @Override public Date call() throws Exception { return sdf.parse("20211109"); } }; ExecutorService pool1 = Executors.newFixedThreadPool(10); List<Future<Date>> futureList1 = new ArrayList<>(); for (int i = 0; i < 10; i++) { futureList1.add(pool1.submit(task1)); } for (Future<Date> future : futureList1) { System.out.println(future.get()); } pool1.shutdown(); //================================================================= // DateTimeFormatter dtf = DateTimeFormatter.ofPattern("yyyyMMdd"); // // Callable<LocalDate> task2 = new Callable<LocalDate>() { // @Override // public LocalDate call() throws Exception { // return LocalDate.parse("20211109",dtf); // } // }; // // ExecutorService pool2 = Executors.newFixedThreadPool(10); // List<Future<LocalDate>> futureList2 = new ArrayList<>(); // for (int i = 0; i < 10; i++) { // futureList2.add(pool2.submit(task2)); // } // // for (Future<LocalDate> future : futureList2) { // System.out.println(future.get()); // } // // pool2.shutdown(); } }
运行之后，就出现了线程安全问题。
将代码中的上半部分注释掉，然后打开下半部分的代码，再次运行，线程安全问题就不存在了。
也就是Java8中提供了新一套日期时间API已经解决了线程安全问题。
2.LocalDate
package com.szh.java8.datetime; import java.time.LocalDate; /** * */ public class TestLocalDate { public static void main(String[] args) { LocalDate ld1 = LocalDate.now(); System.out.println(ld1); LocalDate ld2 = LocalDate.of(2021,5,1); System.out.println(ld2); LocalDate ld3 = ld1.plusYears(20); System.out.println(ld3); LocalDate ld4 = ld1.minusMonths(3); System.out.println(ld4); System.out.println(ld1.isBefore(ld2)); System.out.println(ld2.isAfter(ld1)); System.out.println(ld1.isLeapYear()); System.out.println("年：" + ld1.getYear() + ", 月：" + ld1.getMonth() + ", 日：" + ld1.getDayOfMonth()); System.out.println("年：" + ld1.getYear() + ", 月：" + ld1.getMonthValue() + ", 日：" + ld1.getDayOfMonth()); } }
3.LocalTime
package com.szh.java8.datetime; import java.time.LocalTime; /** * */ public class TestLocalTime { public static void main(String[] args) { LocalTime lt1 = LocalTime.now(); System.out.println(lt1); LocalTime lt2 = LocalTime.of(13,14,15); System.out.println(lt2); LocalTime lt3 = lt2.plusHours(3); System.out.println(lt3); LocalTime lt4 = lt2.minusMinutes(14); System.out.println(lt4); System.out.println(lt1.isBefore(lt2)); System.out.println(lt2.isAfter(lt1)); System.out.println("小时：" + lt1.getHour() + ", 分钟：" + lt1.getMinute() + ", 秒：" + lt1.getSecond()); } }
4.LocalDateTime
package com.szh.java8.datetime; import java.time.LocalDateTime; /** * */ public class TestLocalDateTime { public static void main(String[] args) { LocalDateTime ldt1 = LocalDateTime.now(); System.out.println(ldt1); LocalDateTime ldt2 = LocalDateTime.of(2020,5,1,13,14,15); System.out.println(ldt2); LocalDateTime ldt3 = ldt1.plusYears(15); System.out.println(ldt3); LocalDateTime ldt4 = ldt1.minusDays(20); System.out.println(ldt4); System.out.println(ldt1.isBefore(ldt2)); System.out.println(ldt2.isAfter(ldt1)); System.out.println("年：" + ldt2.getYear() + ", 月：" + ldt2.getMonthValue() + ", 日：" + ldt2.getDayOfMonth() + ", 小时：" + ldt2.getHour() + ", 分钟：" + ldt2.getMinute() + ", 秒：" + ldt2.getSecond()); } }
5.Instant
package com.szh.java8.datetime; import java.time.Instant; import java.time.OffsetDateTime; import java.time.ZoneOffset; /** * Instant : 时间戳（使用 Unix 元年 1970年1月1日 00:00:00 所经历的毫秒值） * 默认使用 UTC 时区 */ public class TestInstant { public static void main(String[] args) { Instant instant1 = Instant.now(); System.out.println(instant1); OffsetDateTime odt = instant1.atOffset(ZoneOffset.ofHoursMinutesSeconds(8,16,32)); System.out.println(odt); System.out.println(instant1.getEpochSecond()); System.out.println(instant1.toEpochMilli()); Instant instant2 = Instant.ofEpochSecond(1000); System.out.println(instant2); Instant instant3 = instant1.plusSeconds(30); System.out.println(instant3); Instant instant4 = instant1.minusSeconds(50); System.out.println(instant4); } }
6.Duration、Period
package com.szh.java8.datetime; import java.time.Duration; import java.time.LocalDate; import java.time.LocalTime; import java.time.Period; /** * Period : 用于计算两个“日期”间隔 * Duration : 用于计算两个“时间”间隔 */ public class TestPeriodDuration { public static void main(String[] args) { LocalDate ld1 = LocalDate.now(); LocalDate ld2 = LocalDate.of(2020,5,1); Period period = Period.between(ld2,ld1); System.out.println("两个日期相差：" + period.getYears() + "年，" + period.getMonths() + "个月，" + period.getDays() + "天...."); System.out.println(period.isNegative()); //检查此期间的三个单位是否为负 System.out.println(period.isZero()); //检查此期间的所有三个单位是否为零 System.out.println("--------------------------------------------"); LocalTime lt1 = LocalTime.now(); try { Thread.sleep(2000); } catch (InterruptedException e) { e.printStackTrace(); } LocalTime lt2 = LocalTime.now(); Duration duration = Duration.between(lt1,lt2); System.out.println("两个时间相差：" + duration.toHours() + "个小时，" + duration.toMinutes() + "分钟，" + duration.getSeconds() + "秒...."); System.out.println(duration.isNegative()); //检查此期间的三个单位是否为负 System.out.println(duration.isZero()); //检查此期间的所有三个单位是否为零 } }
7.TestTemporalAdjuster、TestTemporalAdjusters
package com.szh.java8.datetime; import java.time.DayOfWeek; import java.time.LocalDateTime; import java.time.temporal.TemporalAdjusters; /** * TemporalAdjuster : 时间校正器。有时我们可能需要获取例如：将日期调整到“下个周日”等操作。 * TemporalAdjusters : 该类通过静态方法提供了大量的常用 TemporalAdjuster 的实现。 */ public class TestTemporalAdjuster { public static void main(String[] args) { LocalDateTime ldt1 = LocalDateTime.now(); System.out.println(ldt1); LocalDateTime ldt2 = ldt1.withMonth(5); System.out.println(ldt2); LocalDateTime ldt3 = ldt1.with(TemporalAdjusters.next(DayOfWeek.SATURDAY)); System.out.println(ldt3); //自定义：下一个工作日 LocalDateTime ldt4 = ldt1.with((l) -> { LocalDateTime ldt5 = (LocalDateTime) l; DayOfWeek dow = ldt5.getDayOfWeek(); if (dow.equals(DayOfWeek.FRIDAY)) { return ldt5.plusDays(3); } else if (dow.equals(DayOfWeek.SATURDAY)) { return ldt5.plusDays(2); } else { return ldt5.plusDays(1); } }); System.out.println(ldt4); } }
8.DateTimeFormatter
package com.szh.java8.datetime; import java.time.LocalDateTime; import java.time.format.DateTimeFormatter; /** * 解析与格式化 */ public class TestDateTimeFormatter { public static void main(String[] args) { DateTimeFormatter dtf1 = DateTimeFormatter.ISO_LOCAL_DATE_TIME; LocalDateTime ldt1 = LocalDateTime.now(); String strDate1 = ldt1.format(dtf1); System.out.println(strDate1); System.out.println("-----------------------------------"); DateTimeFormatter dtf2 = DateTimeFormatter.ofPattern("yyyy年MM月dd日 HH:mm:ss"); String strDate2 = ldt1.format(dtf2); System.out.println(strDate2); System.out.println("-----------------------------------"); LocalDateTime newDate = ldt1.parse(strDate2, dtf2); System.out.println(newDate); } }
