JAVA8-Date and Time API： LocalDate, LocalTime, Instant, Duration, Period JAVA8-Date and Time API： LocalDate, LocalTime, Instant, Duration, Period旧API问题1、代码不清晰，一下看不出要转换的日期。2、Date日期中还包含了时间 3、多线程情况下会报错。代码重现：package com.example.study.java8.datetime; import java.text.ParseException; import java.text.SimpleDateFormat; import java.util.Date; public class DateTest { public static void main(String[] args) throws ParseException { //122格林威治时间 11月 23日期 //问题：不能清晰表示日期 Date date = new Date(122, 11, 23); System.out.println(date); //多线程情况下会出现一些问题： //30个线程，每个线程下循环100次，执行时间格式转换。 SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMdd"); for (int i = 0; i < 30; i++) { new Thread(() -> { for (int j = 0; j < 100; j++) { Date parseDate = null; try { parseDate = sdf.parse("20221123"); } catch (ParseException e) { e.printStackTrace(); } System.out.println(parseDate); } }).start(); } } }输出结果：Fri Dec 23 00:00:00 CST 2022 .。。。。。。。。。。 java.lang.NumberFormatException: For input string: "" at java.base/java.lang.NumberFormatException.forInputString(NumberFormatException.java:65) at java.base/java.lang.Long.parseLong(Long.java:702) at java.base/java.lang.Long.parseLong(Long.java:817) at java.base/java.text.DigitList.getLong(DigitList.java:195) at java.base/java.text.DecimalFormat.parse(DecimalFormat.java:2121) at java.base/java.text.SimpleDateFormat.subParse(SimpleDateFormat.java:1931) at java.base/java.text.SimpleDateFormat.parse(SimpleDateFormat.java:1541) at java.base/java.text.DateFormat.parse(DateFormat.java:393) at com.example.study.java8.datetime.DateTest.lambda$main$0(DateTest.java:22) at java.base/java.lang.Thread.run(Thread.java:834) Exception in thread "Thread-25" Exception in thread "Thread-14" java.lang.NumberFormatException: multiple points at java.base/jdk.internal.math.FloatingDecimal.readJavaFormatString(FloatingDecimal.java:1914) at java.base/jdk.internal.math.FloatingDecimal.parseDouble(FloatingDecimal.java:110)新API学习1、LocalDate 线程安全package com.example.study.java8.datetime; import java.text.ParseException; import java.text.SimpleDateFormat; import java.time.LocalDate; import java.time.temporal.ChronoField; import java.util.Date; /** * java8 Date and Time API：LocalDate 线程安全 */ public class DateTestApi { public static void main(String[] args) { testLocalDate(); } private static void testLocalDate() { //1、LocalDate LocalDate localDate = LocalDate.of(2022, 11, 23); System.out.println(localDate); //获取年 System.out.println(localDate.getYear()); //获取月 System.out.println(localDate.getMonth()); //今年的第几天 System.out.println(localDate.getDayOfYear()); //这个月的第几天 System.out.println(localDate.getDayOfMonth()); //这一周的星期几 System.out.println(localDate.getDayOfWeek()); //整数：这个月的第几天 //其它枚举值用法一样 int dayOfMoth = localDate.get(ChronoField.DAY_OF_MONTH); System.out.println(dayOfMoth); //获取当前时间 LocalDate nowLocalDate = LocalDate.now(); System.out.println(nowLocalDate); } }输出结果：2022-11-23 2022 NOVEMBER 327 23 WEDNESDAY 23 2022-11-232、LocalTimepackage com.example.study.java8.datetime; import java.text.ParseException; import java.text.SimpleDateFormat; import java.time.LocalDate; import java.time.LocalTime; import java.time.temporal.ChronoField; import java.util.Date; /** * java8 Date and Time API：LocalDate 线程安全 */ public class DateTestApi { public static void main(String[] args) { testLocalTime(); } private static void testLocalTime(){ //获取当前时间 LocalTime time = LocalTime.now(); System.out.println(time); //时 System.out.println(time.getHour()); //分 System.out.println(time.getMinute()); //秒 System.out.println(time.getSecond()); } }输出结果：21:19:22.856586500 21 19 223、LocalDateTime，提供的api更丰富，线程更安全package com.example.study.java8.datetime; import java.text.ParseException; import java.text.SimpleDateFormat; import java.time.LocalDate; import java.time.LocalDateTime; import java.time.LocalTime; import java.time.temporal.ChronoField; import java.util.Date; /** * java8 Date and Time API：LocalDate 线程安全 */ public class DateTestApi { public static void main(String[] args) { combineLocalDateAndTime(); } // API-2: LocalDateTime 日期时间 private static void combineLocalDateAndTime() { // 整合LocalDate和LocalTIme LocalDate date = LocalDate.now(); LocalTime time = LocalTime.now(); LocalDateTime dateTime = LocalDateTime.of(date, time); System.out.println(dateTime); //直接获取当前日期时间 LocalDateTime now = LocalDateTime.now(); System.out.println(now); //获取日期时间，是一周中的周几，其它api方法用法一样 System.out.println(now.getDayOfWeek()); } }输出结果：2022-11-23T21:28:37.228619600 2022-11-23T21:28:37.229621100 WEDNESDAY4、Instant 点，时刻，时间点package com.example.study.java8.datetime; import java.text.ParseException; import java.text.SimpleDateFormat; import java.time.*; import java.time.temporal.ChronoField; import java.util.Date; /** * java8 Date and Time API：LocalDate 线程安全 */ public class DateTestApi { public static void main(String[] args) throws InterruptedException { testInstant(); } //API-4 Instant 时间点，时刻，点 private static void testInstant() throws InterruptedException { Instant start = Instant.now(); Thread.sleep(1000L); Instant end = Instant.now(); //Duration 时间段 Duration duration = Duration.between(start, end); System.out.println(duration.toMillis()); } }输出结果：10095、Duration 时间段package com.example.study.java8.datetime; import java.text.ParseException; import java.text.SimpleDateFormat; import java.time.*; import java.time.temporal.ChronoField; import java.util.Date; /** * java8 Date and Time API：LocalDate 线程安全 */ public class DateTestApi { public static void main(String[] args) throws InterruptedException { testDuration(); } //API-5 Duration 时间段 private static void testDuration() { LocalTime start = LocalTime.now(); //减1小时 LocalTime end = start.minusHours(1); //开始到结束 Duration durationBetween = Duration.between(end, start); //用了多少小时 System.out.println(durationBetween.toHours()); } } 输出结果：16、Period 周期、时期、时代package com.example.study.java8.datetime; import java.text.ParseException; import java.text.SimpleDateFormat; import java.time.*; import java.time.temporal.ChronoField; import java.util.Date; /** * java8 Date and Time API：LocalDate 线程安全 */ public class DateTestApi { public static void main(String[] args) throws InterruptedException { testPeriod(); } //API-6 Period private static void testPeriod() { Period period = Period.between(LocalDate.of(2000, 10, 9), LocalDate.of(2022, 12, 13)); System.out.println(period.getYears()); System.out.println(period.getMonths()); System.out.println(period.getDays()); } } 输出结果：22 2 47、format 日期时间格式化成字符串package com.example.study.java8.datetime; import java.text.Format; import java.text.ParseException; import java.text.SimpleDateFormat; import java.time.*; import java.time.format.DateTimeFormatter; import java.time.temporal.ChronoField; import java.util.Date; /** * java8 Date and Time API：LocalDate 线程安全 */ public class DateTestApi { public static void main(String[] args) throws InterruptedException { testLocalDateFormat(); } //API-7 format 日期时间格式化成字符串 private static void testLocalDateFormat() { //日期格式化 LocalDate date = LocalDate.now(); String basicDate = date.format(DateTimeFormatter.BASIC_ISO_DATE); //日期时间格式化 LocalDateTime now = LocalDateTime.now(); String time = now.format(DateTimeFormatter.ISO_LOCAL_TIME); System.out.println(basicDate); System.out.println(time); //自定义格式化格式 LocalDateTime localDateTime = LocalDateTime.now(); //自定义格式 DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss"); String formatDateTIme = localDateTime.format(formatter); System.out.println(formatDateTIme); } } 输出结果：20221124 20:28:09.71863167、parse 字符串格式化成日期时间package com.example.study.java8.datetime; import java.text.Format; import java.text.ParseException; import java.text.SimpleDateFormat; import java.time.*; import java.time.format.DateTimeFormatter; import java.time.temporal.ChronoField; import java.util.Date; /** * java8 Date and Time API：LocalDate 线程安全 */ public class DateTestApi { public static void main(String[] args) throws InterruptedException { testLocalDateParse(); } //API-7 parse 字符串转日期时间格式 private static void testLocalDateParse() { //字符串日期转date类型，注意字符串格式和要转换的格式要一样 String date = "2022-11-24"; DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd"); LocalDate localDate = LocalDate.parse(date, formatter); System.out.println(localDate); //字符串时间转time类型，注意字符串格式和要转换的格式要一样 String time = "20:38:24"; DateTimeFormatter timeFormatter = DateTimeFormatter.ofPattern("HH:mm:ss"); LocalTime localTime = LocalTime.parse(time, timeFormatter); System.out.println(localTime); //字符串日期时间转datetime类型，注意字符串格式和要转换的格式要一样 String dateTime = "2022/11/24 20:59:24"; DateTimeFormatter dateTimeFormatter = DateTimeFormatter.ofPattern("yyyy/MM/dd HH:mm:ss"); LocalDateTime localDateTime = LocalDateTime.parse(dateTime, dateTimeFormatter); System.out.println(localDateTime); } } 输出结果：2022-11-24 20:38:24 2022-11-24T20:59:24java.time：更多API可以根据需要查看该包下的时间工具类。