java8中新的Date和Time詳解

更新時間：2016年07月06日 16:18:22 投稿：lqh

這篇文章主要是java8中新的Date和Time,探討新Date類和Time類背后的設計原則，有所需要的小伙伴希望能幫助到你

新Date類和Time類背后的設計原則：

不可變類

java8之前，Date類都是可變類。當我們在多線程環(huán)境下使用它，編程人員應該確認Date對象的線程安全。Java8的Date和Time API提供了線程安全的不可變類。編程人員不用考慮并發(fā)的問題。

領域模型驅(qū)動設計方法

新的日期和時間的類別遵循“域驅(qū)動設計”。對于開發(fā)者來說，理解方法和類的功能是很容易的。

接下來讓我們來看看新Date和Time API:

1.java.time.LocalDate:

LocalDate只提供日期不提供時間信息。它是不可變類且線程安全的。

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只提供時間而不提供日期信息，它是不可變類且線程安全的。

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提供時間和日期的信息，它是不可變類且線程安全的

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，它是不可變類且線程安全的。

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是用來計算兩個給定的日期之間包含多少秒，多少毫秒，它是不可變類且線程安全的

6.java.time.Period:

Period是用來計算兩個給定的日期之間包含多少天，多少月或者多少年，它是不可變類且線程安全的

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());
 }
}

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