java8中新的Date和Time详解_JAVA教程

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:

1.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"));

									 }

									}

2.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));

									 }

									}

3.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));

									 }

									}

4.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());

									 }

									}

5.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

6.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());

									 }

									}