java8 日期时间类

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发布时间：2019-05-27

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Instant：瞬时实例。

LocalDate：本地日期，不包含具体时间例如：2014-01-14 可以用来记录生日、纪念日、加盟日等。

LocalTime：本地时间，不包含日期。

LocalDateTime：组合了日期和时间，但不包含时差和时区信息。

ZonedDateTime：最完整的日期时间，包含时区和相对UTC或格林威治的时差。
新API还引入了 ZoneOffSet 和 ZoneId 类，使得解决时区问题更为简便。解析、格式化时间的 DateTimeFormatter 类也全部重新设计。

常用API

LocalDate

获取年月日:

getYear,getMonthValue,getDayOfMonth

生成特定日期:

LocalDate.of(2018, 01, 21);

判断日期相等:

date1.equals(date2)

比较日期先后:

isBefore() 和 isAfter()

检查闰年:

today.isLeapYear()

格式化:

LocalDate.parse(dayAfterTommorrow, DateTimeFormatter.BASIC_ISO_DATE);

MonthDay和YearMonth

只包含月日或者年月的类,是不可变并且线程安全的值类型。

可以用来判断不同日期所在的月日或者年月是否相等:

MonthDay day1= MonthDay.of(date1.getMonth(), date1.getDayOfMonth());MonthDay day2= MonthDay.from(date2);boolean eq = day1.equals(day2);YearMonth.now().lengthOfMonth(); // 获取当前月的天数YearMonth month = YearMonth.of(2028, Month.FEBRUARY); // 生成年月对象

LocalTime

只有时间没有日期,默认的格式是hh:mm:ss:nnn。

加时:

这些方法返回一个全新的LocalTime实例

LocalTime time = LocalTime.now();LocalTime newTime = time.plusHours(2); // 增加两小时

ChronoUnit 时间单位

枚举类,包含年月日时分秒毫秒等枚举值,可以结合LocalDate和LocalTime等类修改时间:

LocalDate nextWeek = today.plus(1, ChronoUnit.WEEKS);    // 一周后的日期LocalDate previousYear = today.minus(1, ChronoUnit.YEARS); // 一年前的今天

Clock时钟类

用于获取当前时间戳:

Clock clock = Clock.systemUTC();System.out.println(clock.millis());

Period 时间间隔

Period period= Period.between(date1, date2);int days = period.getDays();int months = period.getMonths();int years = period.getYears();

import java.time.Clock;import java.time.Instant;import java.time.LocalDate;import java.time.LocalDateTime;import java.time.LocalTime;import java.time.Month;import java.time.MonthDay;import java.time.OffsetDateTime;import java.time.ZoneOffset;import java.time.Period;import java.time.YearMonth;import java.time.ZoneId;import java.time.ZonedDateTime;import java.time.format.DateTimeFormatter;import java.time.temporal.ChronoUnit;import java.util.Date;public class DateTest {
       //获取今天的日期    public void getCurrentDate(){
           LocalDate today = LocalDate.now();        System.out.println("Today's Local date : " + today);        //这个是作为对比        Date date = new Date();        System.out.println(date);    }    //获取年、月、日信息    public void getDetailDate(){
           LocalDate today = LocalDate.now();        int year = today.getYear();        int month = today.getMonthValue();        int day = today.getDayOfMonth();        System.out.printf("Year : %d  Month : %d  day : %d t %n", year, month, day);    }    //处理特定日期    public void handleSpecilDate(){
           LocalDate dateOfBirth = LocalDate.of(2018, 01, 21);        System.out.println("The specil date is : " + dateOfBirth);    }    //判断两个日期是否相等    public void compareDate(){
           LocalDate today = LocalDate.now();        LocalDate date1 = LocalDate.of(2018, 01, 21);        if(date1.equals(today)){
               System.out.printf("TODAY %s and DATE1 %s are same date %n", today, date1);        }    }    //处理周期性的日期    public void cycleDate(){
           LocalDate today = LocalDate.now();        LocalDate dateOfBirth = LocalDate.of(2018, 01, 21);        MonthDay birthday = MonthDay.of(dateOfBirth.getMonth(), dateOfBirth.getDayOfMonth());        MonthDay currentMonthDay = MonthDay.from(today);        if(currentMonthDay.equals(birthday)){
              System.out.println("Many Many happy returns of the day !!");        }else{
              System.out.println("Sorry, today is not your birthday");        }    }    //获取当前时间    public void getCurrentTime(){
           LocalTime time = LocalTime.now();        System.out.println("local time now : " + time);    }    //增加小时    public void plusHours(){
           LocalTime time = LocalTime.now();        LocalTime newTime = time.plusHours(2); // 增加两小时        System.out.println("Time after 2 hours : " +  newTime);    }    //如何计算一周后的日期    public void nextWeek(){
           LocalDate today = LocalDate.now();        LocalDate nextWeek = today.plus(1, ChronoUnit.WEEKS);        System.out.println("Today is : " + today);        System.out.println("Date after 1 week : " + nextWeek);    }    //计算一年前或一年后的日期    public void minusDate(){
           LocalDate today = LocalDate.now();        LocalDate previousYear = today.minus(1, ChronoUnit.YEARS);        System.out.println("Date before 1 year : " + previousYear);        LocalDate nextYear = today.plus(1, ChronoUnit.YEARS);        System.out.println("Date after 1 year : " + nextYear);    }    public void clock(){
           // 根据系统时间返回当前时间并设置为UTC。        Clock clock = Clock.systemUTC();        System.out.println("Clock : " + clock);        // 根据系统时钟区域返回时间        Clock defaultClock = Clock.systemDefaultZone();        System.out.println("Clock : " + clock);    }    //如何用Java判断日期是早于还是晚于另一个日期    public void isBeforeOrIsAfter(){
           LocalDate today = LocalDate.now();        LocalDate tomorrow = LocalDate.of(2018, 1, 29);        if(tomorrow.isAfter(today)){
               System.out.println("Tomorrow comes after today");        }        LocalDate yesterday = today.minus(1, ChronoUnit.DAYS);        if(yesterday.isBefore(today)){
               System.out.println("Yesterday is day before today");        }    }    //时区处理    public void getZoneTime(){
           //设置时区        ZoneId america = ZoneId.of("America/New_York");        LocalDateTime localtDateAndTime = LocalDateTime.now();        ZonedDateTime dateAndTimeInNewYork  = ZonedDateTime.of(localtDateAndTime, america );        System.out.println("现在的日期和时间在特定的时区 : " + dateAndTimeInNewYork);    }    //使用 YearMonth类处理特定的日期    public void checkCardExpiry(){
           YearMonth currentYearMonth = YearMonth.now();        System.out.printf("Days in month year %s: %d%n", currentYearMonth, currentYearMonth.lengthOfMonth());        YearMonth creditCardExpiry = YearMonth.of(2028, Month.FEBRUARY);        System.out.printf("Your credit card expires on %s %n", creditCardExpiry);    }    //检查闰年    public void isLeapYear(){
           LocalDate today = LocalDate.now();        if(today.isLeapYear()){
              System.out.println("This year is Leap year");        }else {
               System.out.println("2018 is not a Leap year");        }    }    //计算两个日期之间的天数和月数    public void calcDateDays(){
           LocalDate today = LocalDate.now();        LocalDate java8Release = LocalDate.of(2018, Month.MAY, 14);        Period periodToNextJavaRelease = Period.between(today, java8Release);        System.out.println("Months left between today and Java 8 release : "                                           + periodToNextJavaRelease.getMonths() );    }    // 包含时差信息的日期和时间    public void ZoneOffset(){
           LocalDateTime datetime = LocalDateTime.of(2018, Month.FEBRUARY, 14, 19, 30);        ZoneOffset offset = ZoneOffset.of("+05:30");        OffsetDateTime date = OffsetDateTime.of(datetime, offset);        System.out.println("Date and Time with timezone offset in Java : " + date);    }    // 获取时间戳    public void getTimestamp(){
           Instant timestamp = Instant.now();        System.out.println("What is value of this instant " + timestamp);    }    // 使用预定义的格式化工具去解析或格式化日期    public void formateDate(){
           String dayAfterTommorrow = "20180210";        LocalDate formatted = LocalDate.parse(dayAfterTommorrow, DateTimeFormatter.BASIC_ISO_DATE);        System.out.printf("Date generated from String %s is %s %n", dayAfterTommorrow, formatted);    }    public static void main(String[] args) {
           DateTest dt = new DateTest();        dt.formateDate();    }}