新时间日期 API

野性酷女 2022-05-17 03:14 159阅读 0赞

###  传统时间格式化的线程安全问 ###

package com.dongguo.java8.date;
    
    import java.text.SimpleDateFormat;
    import java.util.ArrayList;
    import java.util.Date;
    import java.util.List;
    import java.util.concurrent.*;
    
    
    /**
     * @author Dongguo
     * @date 2021/8/15 0015-13:38
     * @description:java8之前时间格式化方式
     */
    public class TestSimpleDateFormat {
        public static void main(String[] args) throws Exception {
            SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMdd");
    
            Callable<Date> task = new Callable<Date>() {
                @Override
                public Date call() throws Exception {
                    return sdf.parse("20210816");
                }
    
            };
            ExecutorService pool = Executors.newFixedThreadPool(10);
            List<Future<Date>> results =new ArrayList<>();
            for (int i = 0; i < 10; i++) {
                //模拟并发SimpleDateFormat
                results.add(pool.submit(task));
            }
            for (Future<Date> future:results) {
                System.out.println(future.get());
            }
        }
    }

运行会发生安全问题报错

Mon Aug 16 00:00:00 CST 2021
    Mon Aug 16 00:00:00 CST 2021
    Mon Aug 16 00:00:00 CST 2021
    Mon Aug 16 00:00:00 CST 2021
    Mon Aug 16 00:00:00 CST 2021
    Mon Aug 16 00:00:00 CST 2021
    Mon Aug 16 00:00:00 CST 2021
    Exception in thread "main" java.util.concurrent.ExecutionException: java.lang.NumberFormatException: multiple points
    	at java.util.concurrent.FutureTask.report(FutureTask.java:122)
    	at java.util.concurrent.FutureTask.get(FutureTask.java:192)
    	at com.dongguo.java8.date.TestSimpleDateFormat.main(TestSimpleDateFormat.java:33)
    Caused by: java.lang.NumberFormatException: multiple points
    	at sun.misc.FloatingDecimal.readJavaFormatString(FloatingDecimal.java:1890)
    	at sun.misc.FloatingDecimal.parseDouble(FloatingDecimal.java:110)
    	at java.lang.Double.parseDouble(Double.java:538)
    	at java.text.DigitList.getDouble(DigitList.java:169)
    	at java.text.DecimalFormat.parse(DecimalFormat.java:2089)
    	at java.text.SimpleDateFormat.subParse(SimpleDateFormat.java:2162)
    	at java.text.SimpleDateFormat.parse(SimpleDateFormat.java:1514)
    	at java.text.DateFormat.parse(DateFormat.java:364)
    	at com.dongguo.java8.date.TestSimpleDateFormat$1.call(TestSimpleDateFormat.java:22)
    	at com.dongguo.java8.date.TestSimpleDateFormat$1.call(TestSimpleDateFormat.java:19)
    	at java.util.concurrent.FutureTask.run(FutureTask.java:266)
    	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
    	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
    	at java.lang.Thread.run(Thread.java:748)

Java8之前的解决方法：

使用ThreadLocal解决SimpleDateFormat线程安全问题

package com.dongguo.java8.date;
    
    import java.text.DateFormat;
    import java.text.ParseException;
    import java.text.SimpleDateFormat;
    import java.util.Date;
    
    /**
     * @author Dongguo
     * @date 2021/8/16 0016-8:35
     * @description:
     */
    public class DateFormatThreadLocal {
        private static final ThreadLocal<DateFormat> df = new ThreadLocal<DateFormat>(){
            protected DateFormat initialValue(){
                return new SimpleDateFormat("yyyyMMdd");
            }
        };
        public static Date convert(String source) throws ParseException {
            return df.get().parse(source);
        }
    }

package com.dongguo.java8.date;
    
    import org.junit.jupiter.api.Test;
    
    import java.text.ParseException;
    import java.text.SimpleDateFormat;
    import java.util.ArrayList;
    import java.util.Date;
    import java.util.List;
    import java.util.concurrent.*;
    
    
    /**
     * @author Dongguo
     * @date 2021/8/15 0015-13:38
     * @description:java8之前时间格式化方式
     */
    public class TestSimpleDateFormat {
        public static void main(String[] args) throws Exception {
            Callable<Date> task = new Callable<Date>() {
                @Override
                public Date call() throws Exception {
                    return DateFormatThreadLocal.convert("20210816");
                }
    
            };
            ExecutorService pool = Executors.newFixedThreadPool(10);
            List<Future<Date>> results =new ArrayList<>();
            for (int i = 0; i < 10; i++) {
                //模拟并发SimpleDateFormat
                results.add(pool.submit(task));
            }
            for (Future<Date> future:results) {
                System.out.println(future.get());
            }
        }
    }
    运行结果：
    Mon Aug 16 00:00:00 CST 2021
    Mon Aug 16 00:00:00 CST 2021
    Mon Aug 16 00:00:00 CST 2021
    Mon Aug 16 00:00:00 CST 2021
    Mon Aug 16 00:00:00 CST 2021
    Mon Aug 16 00:00:00 CST 2021
    Mon Aug 16 00:00:00 CST 2021
    Mon Aug 16 00:00:00 CST 2021
    Mon Aug 16 00:00:00 CST 2021
    Mon Aug 16 00:00:00 CST 2021

JAVA8之后可以使用

package com.dongguo.java8.date;
    
    import org.junit.jupiter.api.Test;
    
    import java.text.ParseException;
    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.*;
    
    
    /**
     * @author Dongguo
     * @date 2021/8/15 0015-13:38
     * @description:java8时间格式化方式
     */
    public class TestSimpleDateFormat {
        public static void main(String[] args) throws Exception {
            //java8 时间格式化方式
            DateTimeFormatter dtf =  DateTimeFormatter.ofPattern("yyyyMMdd");
            Callable<LocalDate> task = new Callable<LocalDate>() {
                @Override
                public LocalDate call() throws Exception {
                    return LocalDate.parse("20210816",dtf);
                }
    
            };
            ExecutorService pool = Executors.newFixedThreadPool(10);
            List<Future<LocalDate>> results =new ArrayList<>();
            for (int i = 0; i < 10; i++) {
                //模拟并发SimpleDateFormat
                results.add(pool.submit(task));
            }
            for (Future<LocalDate> future:results) {
                System.out.println(future.get());
            }
        }
    }

### 使用 LocalDate、LocalTime、LocalDateTime ###

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。

注: ISO-8601日历系统是国际标准化组织制定的现代公民的日期和时间的表示法

//LocalDate, LocalTime, LocalDateTime
    @Test
    public void test1() {
        //获得当前时间
        LocalDateTime ldt1 = LocalDateTime.now();
        System.out.println(ldt1);
        //指定时间日期
        LocalDateTime ldt2 = LocalDateTime.of(2021, 01, 01, 23, 59, 59);
        System.out.println(ldt2);
        //日期增加2年
        LocalDateTime ldt3 = ldt1.plusYears(2);
        System.out.println(ldt3);
        //日期减2个月
        LocalDateTime ldt4 = ldt1.minusMonths(2);
        System.out.println(ldt4);
    
        System.out.println(ldt1.getYear());//年
        System.out.println(ldt1.getMonthValue());//月
        System.out.println(ldt1.getDayOfMonth());//日
        System.out.println(ldt1.getHour());//时
        System.out.println(ldt1.getMinute());//分
        System.out.println(ldt1.getSecond());//秒
    }
    运行结果：
    2021-08-16T10:09:37.241
    2021-01-01T23:59:59
    2023-08-16T10:09:37.241
    2021-06-16T10:09:37.241
    2021
    8
    16
    10
    9
    37

### 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

//Instant
    @Test
    public void test2() {
        Instant now = Instant.now();//默认获取UTC时区
        System.out.println(now);//2021-08-16T02:13:27.666Z
        OffsetDateTime odt = now.atOffset(ZoneOffset.ofHours(8));//相差8个时区，偏移8个小时
        System.out.println(odt);
        long milli = now.toEpochMilli();//获得毫秒值
        System.out.println(milli);
    
        Instant instant = Instant.ofEpochSecond(1000);//从Unix元年加上1000s
        System.out.println(instant);
    }
    运行结果
    2021-08-16T02:19:57.160Z
    2021-08-16T10:19:57.160+08:00
    1629080397160
    1970-01-01T00:16:40Z

### 计算日期时间间隔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

Duration

//Duration:计算两个 时间 之间的间隔
        @Test
        public void test3() {
            Instant start = Instant.now();
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            Instant end = Instant.now();
            Duration between = Duration.between(start, end);
    //        System.out.println(between.getSeconds());//秒
            System.out.println(between.toMillis());//毫秒
        }
    运行结果
    1000

Period

//Period:计算两个 日期 之间的间隔
    @Test
    public void test4() {
        LocalDate ld1 = LocalDate.of(2020, 1, 1);
        LocalDate ld2 = LocalDate.now();
        Period period = Period.between(ld1, ld2);
    
        System.out.println(period.getYears());
        System.out.println(period.getMonths());
        System.out.println(period.getDays());
    
    }
    运行结果
    1
    7
    15

### 时间校正器 ###

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。

@Test
    public void test5() {
        LocalDateTime now = LocalDateTime.now();
        System.out.println(now);//2021-08-16T12:41:19.605
        LocalDateTime date1 = now.withDayOfMonth(10);//指定天为10号
        System.out.println(date1);//2021-08-10T12:41:19.605
        LocalDateTime date2 = now.with(TemporalAdjusters.next(DayOfWeek.SUNDAY));//下周的周日
        System.out.println(date2);//2021-08-22T12:41:19.605
    
        //自定义下一个工作日
        LocalDateTime date3 = now.with((d) -> {
            LocalDateTime ldt = (LocalDateTime) d;
            DayOfWeek day = ldt.getDayOfWeek();
            if (day.equals(DayOfWeek.FRIDAY)) {
                return ldt.plusDays(3);//周五 增加3天
            } else if (day.equals(DayOfWeek.SATURDAY)) {
                return ldt.plusDays(2);//周六 增加2天
            } else {
                return ldt.plusDays(1);//其他 增加1天
            }
        });
        System.out.println(date3);//2021-08-17T12:41:19.605
    }

### DateTimeFormatter 格式化时间/日期 ###

@Test
    public void test6() {
        DateTimeFormatter dtf = DateTimeFormatter.ISO_DATE;
        LocalDateTime now = LocalDateTime.now();
        System.out.println(now);//2021-08-16T12:57:59.397
        String date1 = now.format(dtf);
        System.out.println(date1);//2021-08-16
        System.out.println("-----------------------");
        DateTimeFormatter dtf2 = DateTimeFormatter.ofPattern("yyyy年MM月dd日 HH::mm::ss");
        String date2 = now.format(dtf2);
        //String date3 = dtf2.format(now);
        System.out.println(date2);//2021年08月16日 12::57::59
       // System.out.println(date3);//2021年08月16日 12::57::59
        System.out.println("-----------------------");
    
        //将字符串日期转回LocalDateTime
        LocalDateTime newDate = LocalDateTime.parse(date3,dtf2);
        System.out.println(newDate);//2021-08-16T12:57:59
    }

### 时区的处理 ###

Java8 中加入了对时区的支持，带时区的时间为分别为：ZonedDate、ZonedTime、ZonedDateTime其中每个时区都对应着 ID，地区ID都为 “\{区域\}/\{城市\}”的格式  
例如 ：Asia/Shanghai 等  
ZoneId：该类中包含了所有的时区信息  
getAvailableZoneIds() : 可以获取所有时区时区信息  
of(id) : 用指定的时区信息获取 ZoneId 对象

@Test
    public void test7() {
        //获得所有时区
        Set<String> zoneIds = ZoneId.getAvailableZoneIds();
        zoneIds.forEach(System.out::println);
    }

@Test
    public void test8() {
        //指定时区的时间
        LocalDateTime ldt = LocalDateTime.now(ZoneId.of("US/Alaska"));
        System.out.println(ldt);//2021-08-15T21:08:46.406
        //指定时区的时间
        LocalDateTime ldt2 = LocalDateTime.now(ZoneId.of("Asia/Shanghai"));//2021-08-16T13:08:46.403
        //返回指定时区的时间与某个时区相差时区的时间
        ZonedDateTime zdt = ldt2.atZone(ZoneId.of("Chile/Continental"));
        System.out.println(zdt);//2021-08-16T13:08:46.408-04:00[Chile/Continental]
    }