103-java 8新機能(3)-新日付API/繰返し注記

一.元の日付処理
1.SimpleDateFormateスレッドが安全でない
(1)安全でないコード

public static void main(String[] args) throws Exception {
        //1.8               
        SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMdd"); //1.8           ,     
        Callable<Date> task = () -> sdf.parse("20200711"); //     

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

        ExecutorService pool = Executors.newFixedThreadPool(10);

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

        for (Future future : list) {
            System.out.println(future.get());
        }

        pool.shutdown();
    }

(2)java 1.8以前のソリューション

public class TestSimpleDateFormate {

    //1.8   ThreadLocal  
    private static final ThreadLocal<DateFormat> LOCAL = new ThreadLocal<DateFormat>(){
        @Override
        protected DateFormat initialValue() {
            return new SimpleDateFormat("yyyyMMdd");
        }
    };


    public static void main(String[] args) throws Exception {
    
        //1.8       
        Callable<Date> task = () -> LOCAL.get().parse("20200711"); //    .ThreadLocal  

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

        ExecutorService pool = Executors.newFixedThreadPool(10);

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

        for (Future future : list) {
            System.out.println(future.get());
        }

        pool.shutdown();
    }
}

(3)java 1.8のソリューション

 		//1.8             
        DateTimeFormatter dtf = DateTimeFormatter.ofPattern("yyyyMMdd");
        Callable<LocalDate> task = () -> LocalDate.parse("20200711",dtf);


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

        ExecutorService pool = Executors.newFixedThreadPool(10);

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

        for (Future future : list) {
            System.out.println(future.get());
        }

        pool.shutdown();
    

二.JAva 1.8新時間/日付API
時間操作の要件:

任意の時刻を取得する時間

.

現在時刻の関連時刻を取得します.例えば、来月10日、当日10時、来週5日など

計算時間の差

時間と文字列間の変換

1.取得日時

LocalDate:取得日

LocalTime:取得時間

LocalDateTime:取得日+時間

	/**
     * LocalDate :     
     * LocalTime :     
     * LocalDateTime :     +  
     *    API      
     *     
     */
    @Test
    public void test1(){
        //      
        LocalDate now = LocalDate.now();
        System.out.println(now);

        //      
        LocalTime now1 = LocalTime.now();
        System.out.println(now1);

        //      +  
        LocalDateTime now2 = LocalDateTime.now();
        System.out.println(now2);

        //      
        LocalDateTime of = LocalDateTime.of(2021, 1, 31, 22, 22, 22);
        System.out.println("of  :" + of);

        //        , , , , , 
        System.out.println("year:" + now2.getYear());
        System.out.println("month:" + now2.getMonth());
        System.out.println("mothOfDate:" + now2.getDayOfMonth());
        System.out.println("hour:" + now2.getHour());

    }

2.時間の増減

plusYears(10)#10年後

minusDays(3)#3日前

	/**
     *      
     */
    @Test
    public void test2(){
        LocalDateTime now = LocalDateTime.now();
        //         
        //10      
        LocalDateTime localDateTime = now.plusYears(10);
        System.out.println("10     :" + localDateTime);
        //3      
        LocalDateTime localDateTime1 = now.minusDays(3);
        System.out.println("3      " + localDateTime1);
    }

3.タイムスタンプ-->コンピュータの読み込み時間

instant

	 /**
     * Instant
     *     -->        
     */
    @Test
    public void test3(){
        //     UTC      
        Instant instant = Instant.now();
        System.out.println(instant);

        //         
        OffsetDateTime odt = instant.atOffset(ZoneOffset.ofHours(8));
        System.out.println(odt);

        //       
        long l = instant.toEpochMilli();
        System.out.println(l);

        //             
        Instant instant1 = Instant.ofEpochSecond(60);
        System.out.println(instant1);
    }

4.計算間隔

Duration:計算時間間の間隔

Period:2つの日付間の間隔を計算する

/**
     *       
     * Duration:          
     * Period:            
     */
    @Test
    public void test4(){
        //      
        Instant instant = Instant.now();
        //  1000      
        Instant instant1 = instant.minusSeconds(1000);
        //           
        System.out.println(Duration.between(instant,instant1).toMillis());

        //      
        LocalDateTime localDateTime = LocalDateTime.now();
        //  1   
        LocalDateTime localDateTime1 = localDateTime.plusYears(1);
        //          ,    
        System.out.println(Duration.between(localDateTime,localDateTime1).toDays());

        //    instant LocalDateTime     
        //    DateTimeException: Unable to obtain Instant from TemporalAccesso
        //System.out.println(Duration.between(instant,localDateTime1).toDays());
    }

5.TemporalAdjusters時間矯正器
机能:*取得来月何日*取得来周何*取得当月...

	/**
     * TemporalAdjusters      
     *   :
     *         
     *       
     *      ...
     */
    @Test
    public void test5(){
        LocalDateTime localDateTime = LocalDateTime.now();
        System.out.println(localDateTime);

        //      10 
        LocalDateTime localDateTime1 = localDateTime.withDayOfMonth(10);
        System.out.println(localDateTime1);

        //     12 
        LocalDateTime localDateTime2 = localDateTime.withHour(12);
        System.out.println(localDateTime2);

        //         
        LocalDateTime localDateTime3 = localDateTime.with(TemporalAdjusters.next(DayOfWeek.SUNDAY));
        System.out.println(localDateTime3);
    }

6.時間フォーマットDateTimeFormatter

	/**
     * DateTimeFormatter
     *      
     *         ,        
     */
    @Test
    public void test6(){
        DateTimeFormatter formatter = DateTimeFormatter.ISO_DATE;

        //         
        LocalDateTime localDateTime = LocalDateTime.now();
        String s = formatter.format(localDateTime);
        System.out.println(s);

        //     Instant
        /*Instant instant = Instant.now();
        String s1 = formatter.format(instant);
        System.out.println(s1);*/

        //         
        /*TemporalAccessor parse = formatter.parse(s);
        System.out.println(parse);*/
        //  
        DateTimeFormatter formatter1 = DateTimeFormatter.ofPattern("yyyy MM dd  HH:mm:ss");
        String s1 = formatter1.format(LocalDateTime.now());
        System.out.println(s1);

        LocalDateTime parse1 = LocalDateTime.parse(s1, formatter1);
        System.out.println(parse1);

    }

7.タイムゾーンZonedDate/ZoneTime/ZoneDateTime

	/**
     *   
     * ZonedDate/ZoneTime/ZoneDateTime
     */
    @Test
    public void test7(){
        Set<String> set = ZoneId.getAvailableZoneIds();
        set.stream()
                .sorted()
                .parallel()
                .forEach(System.out::println);

        LocalDateTime localDateTime = LocalDateTime.now(ZoneId.of("Asia/Chongqing"));
        System.out.println("      :" + localDateTime);
    }

三.JAva 1.8繰り返し注記
同じ場所で注釈を繰り返し使用することができる.

	@MyAnnotation("hello")
    @MyAnnotation("world")
    public void show(){
        System.out.println("     ");
    }

次の手順に従います.

定義注記

@Repeatable(MyAnnotations.class)  //                 ,            
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.METHOD,ElementType.TYPE,ElementType.PARAMETER})
public @interface MyAnnotation {

    String value() default "  ";
}

注釈容器

を定義する.

@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.METHOD,ElementType.TYPE,ElementType.PARAMETER})
public @interface MyAnnotations {

    //myAnnotation     
    MyAnnotation[] value();
}

業務上注釈

public class TestRepeatAnnotation {

    @Test
    public void  test() throws NoSuchMethodException {
        Class<TestRepeatAnnotation> clazz = TestRepeatAnnotation.class;

        //          MyAnnotation  
        Method show = clazz.getMethod("show");
        MyAnnotation[] annotations = show.getAnnotationsByType(MyAnnotation.class);
        for (int i = 0; i < annotations.length; i++) {
            System.out.println(annotations[i].value());
        }
    }

    @MyAnnotation("hello")
    @MyAnnotation("world")
    public void show(){
        System.out.println("     ");
    }
}

詳細、補足