Java8新特性_日期时间新类 LocalDateLocalTimeLocalDateTime

Posted 2021-02-06 超轶绝尘

 

 

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());
    }

}