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With Java 8, a new Date-Time API is introduced to cover the following drawbacks of old date-time API.
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Not thread safe − java.util.Date is not thread safe, thus developers have to deal with concurrency issue while using date. The new date-time API is immutable and does not have setter methods.
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Poor design − Default Date starts from 1900, month starts from 1, and day starts from 0, so no uniformity. The old API had less direct methods for date operations. The new API provides numerous utility methods for such operations.
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Difficult time zone handling − Developers had to write a lot of code to deal with timezone issues. The new API has been developed keeping domain-specific design in mind.
Java 8 introduces a new date-time API under the package java.time. Following are some of the important classes introduced in java.time package.
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Local − Simplified date-time API with no complexity of timezone handling.
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Zoned − Specialized date-time API to deal with various timezones.
Java Local Date-Time API
LocalDate/LocalTime and LocalDateTime classes simplify the development where timezones are not required. Let”s see them in action.
Example: Local Date-Time API
import java.time.LocalDate; import java.time.LocalTime; import java.time.LocalDateTime; import java.time.Month; public class Java8Tester { public static void main(String args[]) { Java8Tester java8tester = new Java8Tester(); java8tester.testLocalDateTime(); } public void testLocalDateTime() { // Get the current date and time LocalDateTime currentTime = LocalDateTime.now(); System.out.println("Current DateTime: " + currentTime); LocalDate date1 = currentTime.toLocalDate(); System.out.println("date1: " + date1); Month month = currentTime.getMonth(); int day = currentTime.getDayOfMonth(); int seconds = currentTime.getSecond(); System.out.println("Month: " + month +"day: " + day +"seconds: " + seconds); LocalDateTime date2 = currentTime.withDayOfMonth(10).withYear(2012); System.out.println("date2: " + date2); //12 december 2014 LocalDate date3 = LocalDate.of(2014, Month.DECEMBER, 12); System.out.println("date3: " + date3); //22 hour 15 minutes LocalTime date4 = LocalTime.of(22, 15); System.out.println("date4: " + date4); //parse a string LocalTime date5 = LocalTime.parse("20:15:30"); System.out.println("date5: " + date5); } }
It should produce the following output −
Current DateTime: 2014-12-09T11:00:45.457 date1: 2014-12-09 Month: DECEMBERday: 9seconds: 45 date2: 2012-12-10T11:00:45.457 date3: 2014-12-12 date4: 22:15 date5: 20:15:30
Java Zoned Date-Time API
Zoned date-time API is to be used when time zone is to be considered. Let us see them in action.
Example: Zoned Date-Time API
import java.time.ZonedDateTime; import java.time.ZoneId; public class Java8Tester { public static void main(String args[]) { Java8Tester java8tester = new Java8Tester(); java8tester.testZonedDateTime(); } public void testZonedDateTime() { // Get the current date and time ZonedDateTime date1 = ZonedDateTime.parse("2007-12-03T10:15:30+05:30[Asia/Karachi]"); System.out.println("date1: " + date1); ZoneId id = ZoneId.of("Europe/Paris"); System.out.println("ZoneId: " + id); ZoneId currentZone = ZoneId.systemDefault(); System.out.println("CurrentZone: " + currentZone); } }
It should produce the following output −
date1: 2007-12-03T10:15:30+05:00[Asia/Karachi] ZoneId: Europe/Paris CurrentZone: Etc/UTC
Java Chrono Units Enum
java.time.temporal.ChronoUnit enum is added in Java 8 to replace the integer values used in old API to represent day, month, etc. Let us see them in action.
Example: Chrono Units Enum
import java.time.LocalDate; import java.time.temporal.ChronoUnit; public class Java8Tester { public static void main(String args[]) { Java8Tester java8tester = new Java8Tester(); java8tester.testChromoUnits(); } public void testChromoUnits() { //Get the current date LocalDate today = LocalDate.now(); System.out.println("Current date: " + today); //add 1 week to the current date LocalDate nextWeek = today.plus(1, ChronoUnit.WEEKS); System.out.println("Next week: " + nextWeek); //add 1 month to the current date LocalDate nextMonth = today.plus(1, ChronoUnit.MONTHS); System.out.println("Next month: " + nextMonth); //add 1 year to the current date LocalDate nextYear = today.plus(1, ChronoUnit.YEARS); System.out.println("Next year: " + nextYear); //add 10 years to the current date LocalDate nextDecade = today.plus(1, ChronoUnit.DECADES); System.out.println("Date after ten year: " + nextDecade); } }
It should produce the following result −
Current date: 2014-12-10 Next week: 2014-12-17 Next month: 2015-01-10 Next year: 2015-12-10 Date after ten year: 2024-12-10
Java Period and Duration
With Java 8, two specialized classes are introduced to deal with the time differences.
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Period − It deals with date based amount of time.
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Duration − It deals with time based amount of time.
Let us see them in action.
Example: Period and Duration
import java.time.temporal.ChronoUnit; import java.time.LocalDate; import java.time.LocalTime; import java.time.Duration; import java.time.Period; public class Java8Tester { public static void main(String args[]) { Java8Tester java8tester = new Java8Tester(); java8tester.testPeriod(); java8tester.testDuration(); } public void testPeriod() { //Get the current date LocalDate date1 = LocalDate.now(); System.out.println("Current date: " + date1); //add 1 month to the current date LocalDate date2 = date1.plus(1, ChronoUnit.MONTHS); System.out.println("Next month: " + date2); Period period = Period.between(date2, date1); System.out.println("Period: " + period); } public void testDuration() { LocalTime time1 = LocalTime.now(); Duration twoHours = Duration.ofHours(2); LocalTime time2 = time1.plus(twoHours); Duration duration = Duration.between(time1, time2); System.out.println("Duration: " + duration); } }
It should produce the following output −
Current date: 2014-12-10 Next month: 2015-01-10 Period: P-1M Duration: PT2H
Java Temporal Adjusters
TemporalAdjuster is used to perform the date mathematics. For example, get the “Second Saturday of the Month” or “Next Tuesday”. Let us see them in action.
Example: Temporal Adjusters
import java.time.LocalDate; import java.time.temporal.TemporalAdjusters; import java.time.DayOfWeek; public class Java8Tester { public static void main(String args[]) { Java8Tester java8tester = new Java8Tester(); java8tester.testAdjusters(); } public void testAdjusters() { //Get the current date LocalDate date1 = LocalDate.now(); System.out.println("Current date: " + date1); //get the next tuesday LocalDate nextTuesday = date1.with(TemporalAdjusters.next(DayOfWeek.TUESDAY)); System.out.println("Next Tuesday on : " + nextTuesday); //get the second saturday of next month LocalDate firstInYear = LocalDate.of(date1.getYear(),date1.getMonth(), 1); LocalDate secondSaturday = firstInYear.with(TemporalAdjusters.nextOrSame( DayOfWeek.SATURDAY)).with(TemporalAdjusters.next(DayOfWeek.SATURDAY)); System.out.println("Second Saturday on : " + secondSaturday); } }
It should produce the following result −
Current date: 2014-12-10 Next Tuesday on : 2014-12-16 Second Saturday on : 2014-12-13
Backward Compatibility
A toInstant() method is added to the original Date and Calendar objects, which can be used to convert them to the new Date-Time API. Use an ofInstant(Insant,ZoneId) method to get a LocalDateTime or ZonedDateTime object. Let us see them in action.
Example of Backward Compatibility
import java.time.LocalDateTime; import java.time.ZonedDateTime; import java.util.Date; import java.time.Instant; import java.time.ZoneId; public class Java8Tester { public static void main(String args[]) { Java8Tester java8tester = new Java8Tester(); java8tester.testBackwardCompatability(); } public void testBackwardCompatability() { //Get the current date Date currentDate = new Date(); System.out.println("Current date: " + currentDate); //Get the instant of current date in terms of milliseconds Instant now = currentDate.toInstant(); ZoneId currentZone = ZoneId.systemDefault(); LocalDateTime localDateTime = LocalDateTime.ofInstant(now, currentZone); System.out.println("Local date: " + localDateTime); ZonedDateTime zonedDateTime = ZonedDateTime.ofInstant(now, currentZone); System.out.println("Zoned date: " + zonedDateTime); } }
It should produce the following output −
Current date: Wed Dec 10 05:44:06 UTC 2014 Local date: 2014-12-10T05:44:06.635 Zoned date: 2014-12-10T05:44:06.635Z[Etc/UTC]
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