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Java 8 New Date And Time Overview

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Java 8 New Date And Time Overview

A practical introduction to the new and improved Date & Time API in Java 8. If you've not had chance to review or use it yet then start here!

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In this article we will discuss about Java 8 Date/Time API. The new Date/Time API was one of the long pending request from the Java developer community. As the existing Date related API is not developer friendly. With the older versions of Java we used third party date time libraries likeJoda-Time. As part of Java 8, the implementation of  JSR 310 lead by Joda-Time author Stephen Colebourne along with Oracle provided Date and Time API. This will be available under java package java.time

The main reasons behind the new Date and Time API are,

  • Immutability
    • Prior to Java 8, the date classes are mutable. When we are using it as part of multi-threaded environments, developers has to make sure the thread safety of date objects. The Java 8 Date and Time API provides all the immutable classes which are thread safe. Developers are free of concurrency issues.
  • Domain Driven Design Approach
    • The classes of new Date and Time API follows “Domain Driven Design”. For developers, understanding of the functionality of methods  and classes is very easy.

Now, we will see some of the classes and operations of Date and Time API.

java.time.LocalDate:

The LocalDate provides only date with out time information. It is immutable and thread safe. Now, we will demonstrate LocalDate class.

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:

The LocalTime provides only time with out date information. It is immutable and thread safe. Now, we will demonstrate LocalTime class.

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:

The LocalDateTime provides date and time information. It is immutable and thread safe. Now, we will demonstrate LocalDateTime class.

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:

The Year provides year  information. It is immutable and thread safe. Now, we will demonstrate Year class.

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:

The Duration provides quantity or amount of time in terms of seconds and nanoseconds. It is immutable and thread safe. Now, we will demonstrate Duration class.

package orr.smarttechie;

import java.time.Duration;
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) {

   LocalDateTime localDateTime = LocalDateTime.now();

   //Get the duration between two dates
   Duration duration = Duration.between(localDateTime, localDateTime.plus(2, ChronoUnit.DAYS));
   System.out.println(duration.toDays());
  }
}


java.time.Period:

The Duration provides a quantity or amount of time in terms of years, months and days. It is immutable and thread safe. Now, we will demonstrate Period class.

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());
  }
}


Enjoy the new flavor of Java 8’s Date and Time API!

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Topics:
tutorial ,java 8 ,api

Published at DZone with permission of Siva Prasad Rao Janapati, DZone MVB. See the original article here.

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