Java 8 - 时间API

拼搏现实的明天。 2022-10-23 12:41 125阅读 0赞

### 文章目录 ###

*  Pre
 *  模拟SimpleDateFormate线程安全问题
 *  LocalDate
 *  LocalTime
 *  LocalDateTime
 *  Instant
 *  Period
 *  Duration
 *  format
 *  parse

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# Pre #

[并发编程-12线程安全策略之常见的线程不安全类][-12]

--------------------

# 模拟SimpleDateFormate线程安全问题 #

package com.artisan.java8.testDate;
    
    import java.text.ParseException;
    import java.text.SimpleDateFormat;
    import java.time.*;
    import java.time.format.DateTimeFormatter;
    import java.time.temporal.ChronoField;
    import java.util.Date;
    
    /** * @author 小工匠 * @version 1.0 * @description: TODO * @date 2021/3/5 0:22 * @mark: show me the code , change the world */
    public class DateInJava8 { 
    
    
        public static void main(String[] args) throws ParseException, InterruptedException { 
    
            Date date = new Date();
            System.out.println(date);
    
    
            /** * 模拟SimpleDateFormat 的线程安全问题 * * Exception in thread "Thread-30" java.lang.NumberFormatException: multiple points * * Exception in thread "Thread-24" java.lang.NumberFormatException: For input string: "E.250214E4" * */
            SimpleDateFormat sdf = new SimpleDateFormat("YYYY-MM-dd");
    
            for (int i = 0; i < 100; i++) { 
                 new Thread(() -> { 
                     for (int j = 0; j < 20; j++) { 
                         try { 
                             String format = sdf.format(date);
                             Date d = sdf.parse(format);
                             System.out.println(d);
                         } catch (ParseException e) { 
                             e.printStackTrace();
                         }
                     }
                 }).start();
            }
    
    
        }
    
    
    }

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3lhbmdzaGFuZ3dlaQ_size_16_color_FFFFFF_t_70 1]

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# LocalDate #

[https://nowjava.com/docs/java-api-11/java.base/java/time/LocalDate.html][https_nowjava.com_docs_java-api-11_java.base_java_time_LocalDate.html]

**LocalDate 是final修饰的不可变类 并且是线程安全的.**

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3lhbmdzaGFuZ3dlaQ_size_16_color_FFFFFF_t_70 2]

*  Java LocalDate is immutable class and hence thread safe.
 *  LocalDate provides date output in the format of YYYY-MM-dd.  
    ![在这里插入图片描述][20210305154148356.png]
 *  The LocalDate class has no time or Timezone data. So LocalDate is suitable to represent dates such as Birthday, National Holiday etc.
 *  LocalDate class implements Temporal, TemporalAdjuster, ChronoLocalDate and Serializable interfaces.
 *  LocalDate is a final class, so we can’t extend it.
 *  LocalDate is a value based class, so we should use equals() method for comparing if two LocalDate instances are equal or not.

public static void testLocalDate(){ 
            LocalDate x = LocalDate.now(); // 日期 2021-03-05
            System.out.println(x);
    
    
            LocalDate lo = LocalDate.of(2021,3,5);
            System.out.println(lo.getYear()); // 年 2021
            System.out.println(lo.getMonth()); // 月 MARCH
            System.out.println(lo.getDayOfMonth()); // 日 5
    
            System.out.println(lo.getDayOfYear()); // 一年中的第几天
            System.out.println(lo.getDayOfMonth());// 一个月中的第几天
            System.out.println(lo.getDayOfWeek());// 礼拜几
    
    
            System.out.println(lo.get(ChronoField.DAY_OF_MONTH));
    
        }

--------------------

# LocalTime #

*  LocalTime provides time without any time zone information. It is very much similar to observing the time from a wall clock which just shown the time and not the time zone information.
 *  The assumption from this API is that all the calendar system uses the same way of representing the time.
 *  It is a value-based class, so use of reference equality (==), identity hash code or synchronization on instances of LocalTime may have - unexpected results and is highly advised to be avoided. The equals method should be used for comparisons.
 *  The LocalTime class is immutable that mean any operation on the object would result in a new instance of LocalTime reference.

private static void testLocalTime() { 
            LocalTime time = LocalTime.now();
            System.out.println(time.getHour());
            System.out.println(time.getMinute());
            System.out.println(time.getSecond());
        }

--------------------

# LocalDateTime #

*  Java LocalDateTime is an immutable class, so it’s thread safe and suitable to use in multithreaded environment.
 *  LocalDateTime provides date and time output in the format of YYYY-MM-DD-hh-mm-ss.zzz, extendable to nanosecond precision. So we can store “2017-11-10 21:30:45.123456789” in LocalDateTime object.  
    ![在这里插入图片描述][20210305163855328.png]
 *  Just like the LocalDate class, LocalDateTime has no time zone data. We can use LocalDateTime instance for general purpose date and time information.
 *  LocalDateTime class implements Comparable, ChronoLocalDateTime, Temporal, TemporalAdjuster, TermporalAccessor and Serializable interfaces.
 *  LocalDateTime is a final class, so we can’t extend it.
 *  LocalDateTime is a value based class, so we should use equals() method to check if two instances of LocalDateTime are equal or not.
 *  LocalDateTime class is a synergistic ‘combination’ of LocalDate and LocalTime with the contatenated format as shown in the figure above.

private static void testLocalDateTime() { 
            LocalDate localDate = LocalDate.now();
            LocalTime time = LocalTime.now();
    
            LocalDateTime localDateTime = LocalDateTime.of(localDate, time);
            System.out.println(localDateTime.toString());
            LocalDateTime now = LocalDateTime.now();
            System.out.println(now);
        }

--------------------

# Instant #

private static void testInstant() throws InterruptedException { 
            Instant start = Instant.now();
            Thread.sleep(1000L);
            Instant end = Instant.now();
            Duration duration = Duration.between(start, end);
            System.out.println(duration.toMillis());
        }

--------------------

# Period #

private static void testPeriod() { 
            Period period = Period.between(LocalDate.of(2020, 5, 10),LocalDate.of(2021, 3, 4));
            System.out.println(period.getYears());
            System.out.println(period.getMonths());
            System.out.println(period.getDays());
        }

--------------------

# Duration #

private static void testDuration() { 
            LocalTime time = LocalTime.now();
            System.out.println(time);
            LocalTime beforeTime = time.minusHours(2);
            System.out.println(beforeTime);
            Duration duration = Duration.between(beforeTime,time );
            System.out.println(duration.toHours());
        }

--------------------

# format #

private static void testDateFormat() { 
            LocalDate localDate = LocalDate.now();
            String format1 = localDate.format(DateTimeFormatter.BASIC_ISO_DATE);
            System.out.println(format1);
    
            DateTimeFormatter mySelfFormatter = DateTimeFormatter.ofPattern("yyyy-MM-dd");
            String format = localDate.format(mySelfFormatter);
            System.out.println(format);
        }

--------------------

# parse #

private static void testDateParse() { 
            String date1 = "20210305";
            LocalDate localDate = LocalDate.parse(date1, DateTimeFormatter.BASIC_ISO_DATE);
            System.out.println(localDate);
           
    
            DateTimeFormatter mySelfFormatter = DateTimeFormatter.ofPattern("yyyy-MM-dd");
            String date2 = "2021-03-05";
            LocalDate localDate2 = LocalDate.parse(date2, mySelfFormatter);
            System.out.println(localDate2);
        }

--------------------

![在这里插入图片描述][20210305230353727.gif_pic_center]

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[-12]: https://blog.csdn.net/yangshangwei/article/details/87887613?ops_request_misc=%257B%2522request%255Fid%2522%253A%2522161492410316780262564401%2522%252C%2522scm%2522%253A%252220140713.130102334.pc%255Fblog.%2522%257D&request_id=161492410316780262564401&biz_id=0&utm_medium=distribute.pc_search_result.none-task-blog-2~blog~first_rank_v2~rank_v29-20-87887613.pc_v2_rank_blog_default&utm_term=SimpleDateFormat
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[https_nowjava.com_docs_java-api-11_java.base_java_time_LocalDate.html]: https://nowjava.com/docs/java-api-11/java.base/java/time/LocalDate.html
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3lhbmdzaGFuZ3dlaQ_size_16_color_FFFFFF_t_70 2]: /images/20221023/6f07aedc685148539c6ef87aedeb3a49.png
[20210305154148356.png]: /images/20221023/e38df232804b413394c15535abb67af5.png
[20210305163855328.png]: /images/20221023/09fad27b79fb48b5a0510fa383273a8f.png
[20210305230353727.gif_pic_center]: /images/20221023/3f852de48f6c4bbb9385ad1e993f4ec4.png