传统时间格式化的线程安全问题

测试线程安全问题

新建测试类

  1. package com.dance.java8.day01.date;
  3. import java.text.SimpleDateFormat;
  4. import java.util.ArrayList;
  5. import java.util.Date;
  6. import java.util.List;
  7. import java.util.concurrent.*;
  9. public class TestSimpleDateFormat {
  11.     public static void main(String[] args) throws ExecutionException, InterruptedException {
  13.         SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyyMMdd");
  15.         ExecutorService executorService = Executors.newFixedThreadPool(10);
  17.         Callable<Date> callable = () -> simpleDateFormat.parse("20161218");
  19.         List<Future<Date>> list = new ArrayList<>();
  21.         for (int i = 0; i < 10; i++) {
  22.             list.add(executorService.submit(callable));
  23.         }
  25.         for (Future<Date> dateFuture : list) {
  26.             System.out.println(dateFuture.get());
  27.         }
  29.     }
  31. }

测试结果

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.dance.java8.day01.date.TestSimpleDateFormat.main(TestSimpleDateFormat.java:26)
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:2056)
    at java.text.SimpleDateFormat.subParse(SimpleDateFormat.java:1867)
    at java.text.SimpleDateFormat.parse(SimpleDateFormat.java:1514)
    at java.text.DateFormat.parse(DateFormat.java:364)
    at com.dance.java8.day01.date.TestSimpleDateFormat.lambda$main$0(TestSimpleDateFormat.java:17)
    at java.util.concurrent.FutureTask.run(FutureTask.java:266)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
    at java.lang.Thread.run(Thread.java:748)

使用ThreadLocal解决线程安全问题

新建ThreadLocal类

package com.dance.java8.day01.date;

import java.text.DateFormat;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;

public class DateFormatThreadLocal {

    private static final ThreadLocal<DateFormat> dateformat = new ThreadLocal<DateFormat>(){
        @Override
        protected DateFormat initialValue() {
            return new SimpleDateFormat("yyyyMMdd");
        }
    };

    public static Date convert(String source) throws ParseException {
        return dateformat.get().parse(source);
    }

}

修改测试类

package com.dance.java8.day01.date;

import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;
import java.util.concurrent.*;

public class TestSimpleDateFormat {

    public static void main(String[] args) throws ExecutionException, InterruptedException {

//        SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyyMMdd");

        ExecutorService executorService = Executors.newFixedThreadPool(10);

        Callable<Date> callable = () -> DateFormatThreadLocal.convert("20161218");

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

        for (int i = 0; i < 10; i++) {
            list.add(executorService.submit(callable));
        }

        for (Future<Date> dateFuture : list) {
            System.out.println(dateFuture.get());
        }

    }

}

测试结果

Sun Dec 18 00:00:00 CST 2016
Sun Dec 18 00:00:00 CST 2016
Sun Dec 18 00:00:00 CST 2016
Sun Dec 18 00:00:00 CST 2016
Sun Dec 18 00:00:00 CST 2016
Sun Dec 18 00:00:00 CST 2016
Sun Dec 18 00:00:00 CST 2016
Sun Dec 18 00:00:00 CST 2016
Sun Dec 18 00:00:00 CST 2016
Sun Dec 18 00:00:00 CST 2016

使用新的日期API解决线程安全问题

新建测试类

package com.dance.java8.day01.date;

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.*;

public class TestSimpleDateFormatNewApi {

    public static void main(String[] args) throws ExecutionException, InterruptedException {

        ExecutorService executorService = Executors.newFixedThreadPool(10);

        // 格式化类
        DateTimeFormatter dateTimeFormatter = DateTimeFormatter.ofPattern("yyyyMMdd");

        // localDate
        Callable<LocalDate> callable = () -> LocalDate.parse("20161218",dateTimeFormatter);

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

        for (int i = 0; i < 10; i++) {
            list.add(executorService.submit(callable));
        }

        for (Future<LocalDate> dateFuture : list) {
            System.out.println(dateFuture.get());
        }

        executorService.shutdown();

    }

}

测试结果

2016-12-18
2016-12-18
2016-12-18
2016-12-18
2016-12-18
2016-12-18
2016-12-18
2016-12-18
2016-12-18
2016-12-18

新的日期API

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,他们提供了简单的日期或时间,并不包含当前的额时间信息.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

    LocalDateTime

    @Test
public void test1(){
  // 获取当前时间
  LocalDateTime localDateTime = LocalDateTime.now();
  // 打印
  System.out.println("当前时间为:"+localDateTime);

  // 指定日期
  LocalDateTime of = LocalDateTime.of(2021, 12, 4, 17, 49, 12);
  System.out.println("指定日期和时间:"+of);

  // 日期时间计算
  // + 1 day
  System.out.println("添加一天:" + localDateTime.plusDays(1));
  // -1 day
  System.out.println("减去一天:" + localDateTime.plusDays(-1));
  // -3 year
  System.out.println("减去三年:" + localDateTime.minusYears(3));
  // 获取
  System.out.println(localDateTime.getYear());
  System.out.println(localDateTime.getMonthValue());
  System.out.println(localDateTime.getDayOfMonth());
  System.out.println(localDateTime.getHour());
  System.out.println(localDateTime.getMinute());
  System.out.println(localDateTime.getSecond());
}

    执行结果

    当前时间为:2021-12-04T17:56:57.172
指定日期和时间:2021-12-04T17:49:12
添加一天:2021-12-05T17:56:57.172
减去一天:2021-12-03T17:56:57.172
减去三年:2018-12-04T17:56:57.172
2021
12
4
17
56
57

    LocalDate和LocalTime

    参考LocalDateTime

    使用Instant

    Instant

    Instant : 时间戳(以Unix 元年: 1970年1月1日 00:00:00 到某个时间之间的毫秒值)

    @Test
public void test2(){
  Instant now = Instant.now();
  System.out.println("时间为:"+now); // 默认获取UTC 时区 格林尼治时间
  // 小时偏移量计算
  OffsetDateTime offsetDateTime = now.atOffset(ZoneOffset.ofHours(8));
  System.out.println("偏移后的时间:"+offsetDateTime);
  // 转换为毫秒
  System.out.println("毫秒:"+now.toEpochMilli());
  System.out.println("系统:"+System.currentTimeMillis());
  // 偏移开始时间
  Instant instant = Instant.ofEpochSecond(60);
  System.out.println("元年偏移时间:"+instant);
}

    执行结果

    时间为:2021-12-04T10:10:50.324Z
偏移后的时间:2021-12-04T18:10:50.324+08:00
毫秒:1638612650324
系统:1638612650428
元年偏移时间:1970-01-01T00:01:00Z

    使用Duration

    Duration

    @Test
public void test3() throws InterruptedException {
  // 时间间隔
  Instant start = Instant.now();
  Thread.sleep(1000);
  Instant end = Instant.now();
  Duration between = Duration.between(start, end);
  System.out.println("时间间隔为:"+between.getSeconds());

  LocalTime startTime = LocalTime.now();
  Thread.sleep(1000);
  LocalTime endTime = LocalTime.now();
  long seconds = Duration.between(startTime, endTime).getSeconds();
  System.out.println("时间间隔为:" + seconds);
}

    执行结果

    时间间隔为:1
时间间隔为:1

    使用Period

    Period

    @Test
public void test4(){
  LocalDate now = LocalDate.now();
  LocalDate localDate = LocalDate.of(2022,3,4);
  Period between = Period.between(now, localDate);
  System.out.println("日期间隔:"+between);
}

    执行结果

    日期间隔:P3M

    日期的操纵

  • TemporalAdjuster:时间矫正器,有时我们可能需要获取列如:将日期调整到”下个周期”等操作

  • TemporalAdjusters:该类通过静态方法提供了大量的常用TemporalAdjuster的实现

    时间矫正器(TemporalAdjuster)

    ```java @Test public void test5(){ LocalDateTime now = LocalDateTime.now(); System.out.println(“当前时间为:”+now); // 指定日期为几号 LocalDateTime localDateTime = now.withDayOfMonth(10); System.out.println(“with date after:”+localDateTime); // 时间矫正器 // 调整到下周日 LocalDateTime with = now.with(TemporalAdjusters.next(DayOfWeek.SUNDAY)); System.out.println(“下周日为:”+with);

    // 自定义下一个工作日 LocalDateTime workDay = now.with(l -> {

      LocalDateTime work = (LocalDateTime) l;
  DayOfWeek dayOfWeek = work.getDayOfWeek();
  switch (dayOfWeek) {
      case FRIDAY:
          return work.plusDays(3);
      case SATURDAY:
          return work.plusDays(2);
      default:
          return work.plusDays(1);
  }

    });

    System.out.println(“下一个工作日:”+workDay);

}

<a name="JkQir"></a>
### 执行结果
```bash
当前时间为:2021-12-04T21:45:33.042
with date after:2021-12-10T21:45:33.042
下周日为:2021-12-05T21:45:33.042
下一个工作日:2021-12-06T21:45:33.042

使用DateTimeFormatter

DateTimeFormatter

@Test
public void test6(){
    // 使用提供的格式化类
    DateTimeFormatter isoDate = DateTimeFormatter.ISO_DATE;
    LocalDateTime now = LocalDateTime.now();
    String format = now.format(isoDate);
    System.out.println(format);

    // 自定义格式化
    DateTimeFormatter dateTimeFormatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
    String format1 = now.format(dateTimeFormatter);
    System.out.println(format1);
}

执行结果

2021-12-04
2021-12-04 22:19:10

时区的处理

  • Java8中假如了对时区的支持,带时区的时间分别为:

    • 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

    • ZondId:该类中包含了所有的时区信息

      • getAvailableZoneIds():可以获取所有时区的时区信息
      • of(id):用指定的时区信息获取ZoneId对象

        ZonedDateTime

        ```java @Test public void test7(){ // 打印所有时区 // ZoneId.getAvailableZoneIds().forEach(System.out::println); // 指定时区获取时间 LocalDateTime now = LocalDateTime.now(ZoneId.of(“Asia/Shanghai”)); System.out.println(now);

      // 获取携带时区 ZonedDateTime zonedDateTime = now.atZone(ZoneId.of(“Asia/Shanghai”)); System.out.println(zonedDateTime); }

      <a name="ZyUrF"></a>
### 执行结果
```bash
2021-12-04T22:39:25.881
2021-12-04T22:39:25.881+08:00[Asia/Shanghai]