Java 8 中新的 Date 和 Time 类入门详解, DateUtil ,以后可以少写几个了,关键是线程安全了

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这篇文章主要是java8中新的Date和Time API的实战。新的Date和Time类是java开发者社区千呼万唤始出来的。Java8 之前存在的Date类一直都受人诟病,很多人都会选择使用第三方的date库joda-time。Java8中的date和time api是jodatime的作者参与开发的,实现了JSR310的全部内容。这些新的api都在包java.time下。

既然第三方的joda-time,date4j都已经足够强大了,为什么java8还要重新实现他呢,一部分的原因是这些第三方的库是存在兼容问题的,比如标准的JSF日期转化器与joda-time api,就不兼容,每次使用都需要编写自己的转换器,所以标准化api是必须的,就有了JSR310,java8中就实现了他全部的规定内容。

新Date类和Time类背后的设计原则:

不可变类

java8之前,Date类都是可变类。当我们在多线程环境下使用它,编程人员应该确认Date对象的线程安全。Java8的Date和Time API提供了线程安全的不可变类。编程人员不用考虑并发的问题。

领域模型驱动设计方法

新的日期和时间的类别遵循“域驱动设计”。对于开发者来说,理解方法和类的功能是很容易的。

接下来让我们来看看新Date和Time API:

java.time.LocalDate:

LocalDate只提供日期不提供时间信息。它是不可变类且线程安全的。

package org.smarttechie;import java.time.LocalDate;import java.time.temporal.ChronoUnit;/*** This class demonstrates JAVA 8 data and time API* @author Siva Prasad Rao Janapati* */public class DateTimeDemonstration {/*** @param args*/public static void main(String[] args) {   //Create date LocalDate localDate = LocalDate.now();    System.out.println("The local date is :: " + localDate);    //Find the length of the month. That is, how many days are there for this month.   System.out.println("The number of days available for this month:: " + localDate.lengthOfMonth());    //Know the month name   System.out.println("What is the month name? :: " + localDate.getMonth().name());    //add 2 days to the today's date.   System.out.println(localDate.plus(2, ChronoUnit.DAYS));    //substract 2 days from today   System.out.println(localDate.minus(2, ChronoUnit.DAYS));    //Convert the string to date   System.out.println(localDate.parse("2017-04-07"));  }}


java.time.LocalTime:

LocalTime只提供时间而不提供日期信息,它是不可变类且线程安全的。

package org.smarttechie;import java.time.LocalTime;import java.time.temporal.ChronoUnit;/*** This class demonstrates JAVA 8 data and time API* @author Siva Prasad Rao Janapati* */public class DateTimeDemonstration {/*** @param args*/public static void main(String[] args) {   //Get local time   LocalTime localTime = LocalTime.now();   System.out.println(localTime);  //Get the hour of the day  System.out.println("The hour of the day:: " + localTime.getHour());  //add 2 hours to the time.  System.out.println(localTime.plus(2, ChronoUnit.HOURS));  //add 6 minutes to the time.  System.out.println(localTime.plusMinutes(6));  //substract 2 hours from current time  System.out.println(localTime.minus(2, ChronoUnit.HOURS)); }}

java.time.LocalDateTime:

LocalDateTime提供时间和日期的信息,它是不可变类且线程安全的

package orr.smarttechie;import java.time.LocalDateTime;import java.time.temporal.ChronoUnit;/*** This class demonstrates JAVA 8 data and time API* @author Siva Prasad Rao Janapati**/public class DateTimeDemonstration {/*** @param args*/public static void main(String[] args) {    //Get LocalDateTime object    LocalDateTime localDateTime = LocalDateTime.now();    System.out.println(localDateTime);    //Find the length of month. That is, how many days are there for this month.    System.out.println("The number of days available for this month:: " + localDateTime.getMonth().length(true));    //Know the month name    System.out.println("What is the month name? :: " + localDateTime.getMonth().name());    //add 2 days to today's date.    System.out.println(localDateTime.plus(2, ChronoUnit.DAYS));    //substract 2 days from today    System.out.println(localDateTime.minus(2, ChronoUnit.DAYS));  }}

java.time.Year:

Year提供年的信息,它是不可变类且线程安全的。

package orr.smarttechie;import java.time.Year;import java.time.temporal.ChronoUnit;/*** This class demonstrates JAVA 8 data and time API* @author Siva Prasad Rao Janapati**/public class DateTimeDemonstration {/*** @param args*/public static void main(String[] args) {   //Get year   Year year = Year.now();   System.out.println("Year ::" + year);   //know the year is leap year or not   System.out.println("Is year[" +year+"] leap year?"+ year.isLeap());  }}

java.time.Duration:

Duration是用来计算两个给定的日期之间包含多少秒,多少毫秒,它是不可变类且线程安全的

java.time.Period:

Period是用来计算两个给定的日期之间包含多少天,多少月或者多少年,它是不可变类且线程安全的

package orr.smarttechie;import java.time.LocalDate;import java.time.Period;import java.time.temporal.ChronoUnit;/*** This class demonstrates JAVA 8 data and time API* @author Siva Prasad Rao Janapati**/public class DateTimeDemonstration {/*** @param args*/public static void main(String[] args) {   LocalDate localDate = LocalDate.now();   Period period = Period.between(localDate, localDate.plus(2, ChronoUnit.DAYS));   System.out.println(period.getDays());  }}

原文链接:http://mp.weixin.qq.com/s?__biz=MjM5Mzk3MzA4MA==&mid=2651366328&idx=2&sn=95dedbbe34c4dca18ff359bd33474792&scene=0

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