Java8_新日期工具类

1. 传统的日期格式器方法(线程不安全)

@Test
public void test() throws Exception{
    //传统时间格式器(线程不安全)
    SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMdd");
    //任务
    Callable<Date> task = () -> sdf.parse("20201001");
    //线程池
    ExecutorService pool = Executors.newFixedThreadPool(10);
    //模拟多线程
    List<Future<Date>> futureList = new ArrayList<>();
    for (int i = 0; i < 10; i++) {
        futureList.add(pool.submit(task));
    }
    //输出结果
    for (Future<Date> dateFuture : futureList) {
        System.out.println(dateFuture.get());
    }
}

//抛出了java.util.concurrent.ExecutionException: java.lang.NumberFormatException: multiple points

2. 传统的日期格式器解决线程安全方法(ThreadLocal)

//1.创建工具类，内部方法由绑定ThreadLocal的SimpleDateFormat提供。
public class SimpleDateFormatThreadLocal {
    //创建一个ThreadLocal对象,并初始值为SimpleDateFormat对象
    public static final ThreadLocal<SimpleDateFormat> sdf = new ThreadLocal<SimpleDateFormat>(){
        protected SimpleDateFormat initialValue() {
            return new SimpleDateFormat("yyyyMMdd");
        }
    };
    //提供一个dateStr转换Date方法
    public static Date convert(String dateStr) throws ParseException {
        return sdf.get().parse(dateStr);
    }
}

//2.测试(线程安全问题解读了)
@Test
public void test1() throws Exception{
    //任务(使用绑定在ThreadLocal上的SimpleDateFormat对象转换)
    Callable<Date> task = () -> SimpleDateFormatThreadLocal.convert("20201020");
    //线程池
    ExecutorService pool = Executors.newFixedThreadPool(10);
    //模拟多线程
    List<Future<Date>> futureList = new ArrayList<>();
    for (int i = 0; i < 10; i++) {
        futureList.add(pool.submit(task));
    }
    //输出结果
    for (Future<Date> dateFuture : futureList) {
        System.out.println(dateFuture.get());
    }
    //关闭线程池
    pool.shutdown();
}

3. LocalDate新日期类(线程安全)

@Test
public void test2() throws Exception{
    //新日期格式器(线程安全)
    DateTimeFormatter dtf = DateTimeFormatter.ofPattern("yyyyMMdd");
    //任务(LocalDate.parse(dateStr,dateTimeFormatter))
    Callable<LocalDate> task = () -> LocalDate.parse("20201020",dtf);
    //线程池
    ExecutorService pool = Executors.newFixedThreadPool(10);
    //模拟多线程
    List<Future<LocalDate>> futureList = new ArrayList<>();
    for (int i = 0; i < 10; i++) {
        futureList.add(pool.submit(task));
    }
    //输出结果
    for (Future<LocalDate> dateFuture : futureList) {
        System.out.println(dateFuture.get());
    }
    //关闭线程池
    pool.shutdown();
}

4. 新日期类、时间戳、时间间隔对象，日期间隔对象

//1.LocalDate LocalTime LocalDateTime 新日期类，类实例是不可变对象
@Test
public void test3(){
    //获取当前日期对象
    LocalDateTime ldt1 = LocalDateTime.now();
    System.out.println(ldt1);

    //获取指定日期对象
    LocalDateTime ldt2 = LocalDateTime.of(2018, 10, 10, 11, 11, 11);
    System.out.println(ldt2);

    //日期对象运算
    LocalDateTime ldt3 = ldt2.plusYears(1);
    System.out.println(ldt3);
    LocalDateTime ldt4 = ldt3.minusMonths(5);
    System.out.println(ldt4);

    //获取日期属性...
    System.out.println("ldt4.getMonthValue() = " + ldt4.getMonthValue());
    System.out.println("ldt4.getHour() = " + ldt4.getHour());
}

//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 test4(){
    //获取当前时间戳对象
    Instant instant = Instant.now();    //默认UTC时区
    System.out.println(instant);

    //偏移量时间对象
    OffsetDateTime offsetDateTime = instant.atOffset(ZoneOffset.ofHours(8)); //+8H 北京时间
    System.out.println(offsetDateTime);

    //获取指定时间戳对象
    Instant instant1 = Instant.ofEpochSecond(60);   //从Unix元年算起的时间戳
    System.out.println(instant1);                   //1970-01-01T00:01:00Z
}

//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 test5() throws InterruptedException {
    //时间间隔对象 Duration
    Instant t1 = Instant.now();
    Thread.sleep(1000);
    Instant t2 = Instant.now();
    Duration duration = Duration.between(t1, t2);
    System.out.println(duration.toMillis());

    //日期间隔对象 Period
    LocalDate d1 = LocalDate.of(2020, 1, 1);
    LocalDate d2 = LocalDate.now();
    Period period = Period.between(d1, d2);
    System.out.println(period.getYears());      //相差年数
    System.out.println(period.getMonths());     //相差月数
    System.out.println(period.getDays());       //相差天数
}

5.时间调整器 TemporaAdjuster

@Test
public void test6(){
    //获取当前时间对象
    LocalDateTime localDateTime = LocalDateTime.now();
    System.out.println(localDateTime);

    //指定月份为2
    LocalDateTime localDateTime1 = localDateTime.withMonth(2);
    System.out.println(localDateTime1);

    //时间调整器工具类TemporalAdjusters.next指定下个周日
    LocalDateTime localDateTime2 = localDateTime.with(TemporalAdjusters.next(DayOfWeek.SUNDAY));
    System.out.println("next Sunday: " + localDateTime2);

    //计算下个工作日(自定义时间调整器)
    LocalDateTime localDateTime4 = localDateTime.with(temporal -> {
        //强转日期类
        LocalDateTime localDateTime3 = (LocalDateTime) temporal;
        //获取周几
        DayOfWeek dayOfWeek = localDateTime3.getDayOfWeek();
        //返回下个工作日
        if(dayOfWeek.equals(DayOfWeek.FRIDAY)){
            return localDateTime3.plusDays(3);
        }else if(dayOfWeek.equals(DayOfWeek.SATURDAY)){
            return localDateTime3.plusDays(2);
        }else {
            return localDateTime3.plusDays(1);
        }
    });
    System.out.println("next workDay: " + localDateTime4);
}

6.时间格式器 DateTimeFormatter

@Test
public void test7(){
    //日期格式器
    DateTimeFormatter dateTimeFormatter = DateTimeFormatter.ofPattern("yyyy年MM月dd日 HH:mm:ss");
    //当前时间对象
    LocalDateTime now = LocalDateTime.now();
    //格式化当前日期 localDateTime => dateStr
    String dateStr = dateTimeFormatter.format(now);
    System.out.println(dateStr);
    //解析日期字符串 dateStr => localDateTime
    LocalDateTime lacalDateTime = LocalDateTime.parse(dateStr, dateTimeFormatter);
    System.out.println(lacalDateTime);
}

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

@Test
public void test8(){
    //获取所有时区字符串表现形式
    Set<String> set = ZoneId.getAvailableZoneIds();
    //set.forEach(System.out::println);
    //设置为亚洲/东京时区时间
    LocalDateTime localDateTime = LocalDateTime.now(ZoneId.of("Asia/Tokyo"));
    System.out.println(localDateTime);
    //为日期对象添加时区信息
    ZonedDateTime zonedDateTime = localDateTime.atZone(ZoneId.of("Asia/Tokyo"));
    System.out.println(zonedDateTime);
}

8.可重复注解

//1. Annotation注解容器
@Target({TYPE, FIELD, METHOD, PARAMETER, CONSTRUCTOR, LOCAL_VARIABLE})
@Retention(RetentionPolicy.RUNTIME)
public @interface MyAnnotations {
    MyAnnotation[] value();
}

//2. Annotation注解  -> @Repeatable(MyAnnotations.class) 指定注解容器 
@Repeatable(MyAnnotations.class)
@Target({TYPE, FIELD, METHOD, PARAMETER, CONSTRUCTOR, LOCAL_VARIABLE})
@Retention(RetentionPolicy.RUNTIME)
public @interface MyAnnotation {
    String value() default "codeDuck";
}

//3. 使用和测试
public class TestAnno {
    //重复注解
    @MyAnnotation("hello")
    @MyAnnotation("world")
    public void demo(){}

    @Test
    public void test() throws NoSuchMethodException {
        //字节码对象
        Class<TestAnno> testAnnoClass = TestAnno.class;
        //获取demo方法对象
        Method demo = testAnnoClass.getMethod("demo");
        //获取MyAnnotation.class类型注解对象
        MyAnnotation[] annotations = demo.getAnnotationsByType(MyAnnotation.class);
        for (MyAnnotation annotation : annotations) {
            System.out.println(annotation.value());  // hello \n world
        }
    }
}

Java8_新日期工具类

1. 传统的日期格式器方法(线程不安全)

2. 传统的日期格式器解决线程安全方法(ThreadLocal)

3. LocalDate新日期类(线程安全)

4. 新日期类、时间戳、时间间隔对象，日期间隔对象

5.时间调整器 TemporaAdjuster

6.时间格式器 DateTimeFormatter

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

8.可重复注解

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