Java8新特性_日期时间新类 LocalDate、LocalTime、LocalDateTime

时间：2022-01-04 02:23:21
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.Callable;

import java.util.concurrent.ExecutionException;

import java.util.concurrent.ExecutorService;

import java.util.concurrent.Executors;

import java.util.concurrent.Future;

public class TestSimpleDateFormat {

    public static void main(String[] args) throws Exception {

//        oldDateMethod();

//        oldDateMethodThreadSafe();

        java8DateMethodThreadSave();

    }

    /**线程不安全，报错*/

    public static void oldDateMethod() throws  Exception{

        SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMdd");

        Callable<Date> task = new Callable<Date>() {

            @Override

            public Date call() throws Exception {

                return sdf.parse("20161121");

            }

        };

        ExecutorService pool = Executors.newFixedThreadPool(10);

        List<Future<Date>> results = new ArrayList<>();

        for (int i = 0; i < 10; i++) {

            results.add(pool.submit(task));

        }

        for (Future<Date> future : results) {

            System.out.println(future.get());

        }

        pool.shutdown();

    }

    //解决多线程安全问题

    public static void oldDateMethodThreadSafe()  throws  Exception{

        Callable<Date> task = new Callable<Date>() {

            @Override

            public Date call() throws Exception {

                return DateFormatThreadLocal.convert("20161121");

            }

        };

        ExecutorService pool = Executors.newFixedThreadPool(10);

        List<Future<Date>> results = new ArrayList<>();

        for (int i = 0; i < 10; i++) {

            results.add(pool.submit(task));

        }

        for (Future<Date> future : results) {

            System.out.println(future.get());

        }

        pool.shutdown();

    }

    /**java8的实现*/

    public static void java8DateMethodThreadSave()  throws  Exception{

        DateTimeFormatter dtf = DateTimeFormatter.ofPattern("yyyyMMdd");

        Callable<LocalDate> task = new Callable<LocalDate>() {

            @Override

            public LocalDate call() throws Exception {

                LocalDate ld = LocalDate.parse("20161121", dtf);

                return ld;

            }

        };

        ExecutorService pool = Executors.newFixedThreadPool(10);

        List<Future<LocalDate>> results = new ArrayList<>();

        for (int i = 0; i < 10; i++) {

            results.add(pool.submit(task));

        }

        for (Future<LocalDate> future : results) {

            System.out.println(future.get());

        }

        pool.shutdown();

    }

}
import java.text.DateFormat;

import java.text.ParseException;

import java.text.SimpleDateFormat;

import java.util.Date;

public class DateFormatThreadLocal {

    private static final ThreadLocal<DateFormat> df = new ThreadLocal<DateFormat>(){

        protected DateFormat initialValue(){

            return new SimpleDateFormat("yyyyMMdd");

        }

    };

    public static final Date convert(String source) throws ParseException {

        return df.get().parse(source);

    }

}

　　LocalDate、LocalTime、LocalDateTime 类的实 例是不可变的对象，分别表示使用 ISO-8601日 历系统的日期、时间、日期和时间。它们提供 了简单的日期或时间，并不包含当前的时间信 息。也不包含与时区相关的信息。

Instant 时间戳

用于“时间戳”的运算。它是以Unix元年(传统 的设定为UTC时区1970年1月1日午夜时分)开始 所经历的描述进行运算

Duration 和 Period

Duration : 用于计算两个“时间”间隔

Period    : 用于计算两个“日期”间隔

import java.time.DayOfWeek;

import java.time.Duration;

import java.time.Instant;

import java.time.LocalDate;

import java.time.LocalDateTime;

import java.time.OffsetDateTime;

import java.time.Period;

import java.time.ZoneId;

import java.time.ZoneOffset;

import java.time.ZonedDateTime;

import java.time.format.DateTimeFormatter;

import java.time.temporal.TemporalAdjusters;

import java.util.Set;

import org.junit.Test;

public class TestLocalDateTime {

    //6.ZonedDate、ZonedTime、ZonedDateTime ： 带时区的时间或日期

    @Test

    public void test7(){

        LocalDateTime ldt = LocalDateTime.now(ZoneId.of("Asia/Shanghai"));

        System.out.println(ldt);

        ZonedDateTime zdt = ZonedDateTime.now(ZoneId.of("US/Pacific"));

        System.out.println(zdt);

    }

    @Test

    public void test6(){

        Set<String> set = ZoneId.getAvailableZoneIds();

        set.forEach(System.out::println);

    }

    //5. DateTimeFormatter : 解析和格式化日期或时间

    @Test

    public void test5(){

//        DateTimeFormatter dtf = DateTimeFormatter.ISO_LOCAL_DATE;

        DateTimeFormatter dtf = DateTimeFormatter.ofPattern("yyyy年MM月dd日 HH:mm:ss E");

        LocalDateTime ldt = LocalDateTime.now();

        String strDate = ldt.format(dtf);

        System.out.println(strDate);

        LocalDateTime newLdt = ldt.parse(strDate, dtf);

        System.out.println(newLdt);

    }

    //4. TemporalAdjuster : 时间校正器

    @Test

    public void test4(){

    LocalDateTime ldt = LocalDateTime.now();

        System.out.println(ldt);

        LocalDateTime ldt2 = ldt.withDayOfMonth(10);

        System.out.println(ldt2);

        LocalDateTime ldt3 = ldt.with(TemporalAdjusters.next(DayOfWeek.SUNDAY));

        System.out.println(ldt3);

        //自定义：下一个工作日

        LocalDateTime ldt5 = ldt.with((l) -> {

            LocalDateTime ldt4 = (LocalDateTime) l;

            DayOfWeek dow = ldt4.getDayOfWeek();

            if(dow.equals(DayOfWeek.FRIDAY)){

                return ldt4.plusDays(3);

            }else if(dow.equals(DayOfWeek.SATURDAY)){

                return ldt4.plusDays(2);

            }else{

                return ldt4.plusDays(1);

            }

        });

        System.out.println(ldt5);

    }

    //3.

    //Duration : 用于计算两个“时间”间隔

    //Period : 用于计算两个“日期”间隔

    @Test

    public void test3(){

        Instant ins1 = Instant.now();

        System.out.println("--------------------");

        try {

            Thread.sleep(1000);

        } catch (InterruptedException e) {

        }

        Instant ins2 = Instant.now();

        System.out.println("所耗费时间为：" + Duration.between(ins1, ins2));

        System.out.println("----------------------------------");

        LocalDate ld1 = LocalDate.now();

        LocalDate ld2 = LocalDate.of(2011, 1, 1);

        Period pe = Period.between(ld2, ld1);

        System.out.println(pe.getYears());

        System.out.println(pe.getMonths());

        System.out.println(pe.getDays());

    }

    //2. 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）

    @Test

    public void test2(){

        Instant ins = Instant.now();  //默认使用 UTC 时区

        System.out.println(ins);

        OffsetDateTime odt = ins.atOffset(ZoneOffset.ofHours(8)); //中国和默认时区差8个小时的时差，（时间偏移量）

        System.out.println(odt);

        System.out.println(ins.getNano());

        Instant ins2 = Instant.ofEpochSecond(5);

        System.out.println(ins2);

    }

    //1. LocalDate、LocalTime、LocalDateTime

    @Test

    public void test1(){

        LocalDateTime ldt = LocalDateTime.now();

        System.out.println(ldt);

        LocalDateTime ld2 = LocalDateTime.of(2016, 11, 21, 10, 10, 10);

        System.out.println(ld2);

        LocalDateTime ldt3 = ld2.plusYears(20);

        System.out.println(ldt3);

        LocalDateTime ldt4 = ld2.minusMonths(2);

        System.out.println(ldt4);

        System.out.println(ldt.getYear());

        System.out.println(ldt.getMonthValue());

        System.out.println(ldt.getDayOfMonth());

        System.out.println(ldt.getHour());

        System.out.println(ldt.getMinute());

        System.out.println(ldt.getSecond());

    }

}

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