文章目录
- Pre
- 模拟SimpleDateFormate线程安全问题
- LocalDate
- LocalTime
- LocalDateTime
- Instant
- Period
- Duration
- format
- parse
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();
}
}
}
LocalDate
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.
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Java LocalDate is immutable class and hence thread safe.
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LocalDate provides date output in the format of YYYY-MM-dd.
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The LocalDate class has no time or Timezone data. So LocalDate is suitable to represent dates such as Birthday, National Holiday etc.
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LocalDate class implements Temporal, TemporalAdjuster, ChronoLocalDate and Serializable interfaces.
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LocalDate is a final class, so we can’t extend it.
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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
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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.
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The assumption from this API is that all the calendar system uses the same way of representing the time.
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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.
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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
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Java LocalDateTime is an immutable class, so it’s thread safe and suitable to use in multithreaded environment.
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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.
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Just like the LocalDate class, LocalDateTime has no time zone data. We can use LocalDateTime instance for general purpose date and time information.
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LocalDateTime class implements Comparable, ChronoLocalDateTime, Temporal, TemporalAdjuster, TermporalAccessor and Serializable interfaces.
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LocalDateTime is a final class, so we can’t extend it.
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LocalDateTime is a value based class, so we should use equals() method to check if two instances of LocalDateTime are equal or not.
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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);
}