Java 8 Date – LocalDate, LocalDateTime, Instant

Java 8 Date Time API is a standout amongst the most looked for after change for engineers. Java has been feeling the loss of a predictable methodology for Date and Time from begin and Java 8 Date Time API is an appreciated expansion deeply Java APIs.

Why do we need new Java Date Time API?

Before we begin taking a gander at the Java 8 Date Time API, how about we see for what reason do we need another API for this. There have been a few issues with the current date and time related classes in java, some of them are:

  1. Java Date Time classes are not characterized reliably, we have Date Class in both java.util just as java.sql bundles. Again arranging and parsing classes are characterized in java.text package.
  2. java.util.Date contains both date and time, while java.sql.Date contains just date. Having this in java.sql bundle doesn't bode well. Additionally both the classes have same name, that is an extremely terrible plan itself.
  3. There are no plainly characterized classes for time, timestamp, designing and parsing. We have java.text.DateFormat conceptual class for parsing and organizing need. Generally SimpleDateFormat class is utilized for parsing and formatting.
  4. All the Date classes are impermanent, so they are not string safe. It's one of the most serious issue with Java Date and Calendar classes.
  5. Date class doesn't give internationalization, there is no timezone support. So java.util.Calendar and java.util.TimeZone classes were presented, yet they additionally have every one of the issues recorded above.

There are some different issues with the techniques characterized in Date and Calendar classes however above issues clarify that a strong Date Time API was required in Java. That is the reason Joda Time assumed a key job as a quality trade for Java Date Time requirements.

Java 8 Date

Java 8 Date Time API is JSR-310 usage. It is intended to conquer every one of the blemishes in the heritage date time usage. A portion of the plan standards of new Date Time API are:

  1. Immutability: All the classes in the new Date Time API are unchanging and useful for multithreaded environments.
  2. Separation of Concerns: The new API isolates plainly between intelligible date time and machine time (unix timestamp). It characterizes separate classes for Date, Time, DateTime, Timestamp, Timezone etc.
  3. Clarity: The strategies are unmistakably characterized and play out a similar activity in every one of the classes. For instance, to get the present case we have now() technique. There are design() and parse() strategies characterized in every one of these classes instead of having a different class for them.

    All the classes use Factory Pattern and Strategy Pattern for better taking care of. When you have utilized the techniques in one of the class, working with different classes won't be hard.

  4. Utility operations: All the new Date Time API classes accompanies strategies to perform normal errands, for example, in addition, short, position, parsing, getting isolated part in date/time etc.
  5. Extendable: The new Date Time API takes a shot at ISO-8601 timetable framework however we can utilize it with other non ISO logbooks as well.

Java 8 Date Time API Packages

Java 8 Date Time API comprises of following packages.

java.time Package: This is the base bundle of new Java Date Time API. All the real base classes are a piece of this bundle, for example, LocalDate, LocalTime, LocalDateTime, Instant, Period, Duration and so on. These classes are permanent and string safe. A large portion of the occasions, these classes will be adequate for dealing with normal requirements.
  • java.time.chrono Package: This bundle characterizes nonexclusive APIs for non ISO schedule frameworks. We can expand AbstractChronology class to make our very own logbook system.
  • java.time.format Package: This bundle contains classes utilized for arranging and parsing date time objects. The vast majority of the occasions, we would not be straightforwardly utilizing them since standard classes in java.time bundle give designing and parsing methods.
  • java.time.temporal Package: This bundle contains fleeting articles and we can utilize it for discover explicit date or time identified with date/time object. For instance, we can utilize these to discover the first or a day ago of the month. You can distinguish these strategies effectively on the grounds that they generally have group "withXXX".
  • java.time.zone Package: This bundle contains classes for supporting distinctive time zones and their rules.
  • Java 8 Date Time API Examples

    We have investigated the vast majority of the essential pieces of Java Date Time API. Now is the ideal time currently to investigate most imperative classes of Date Time API with examples.

    1. LocalDate

      LocalDate is a changeless class that speaks to Date with default arrangement of yyyy-MM-dd. We can utilize now() technique to get the present date. We can likewise give input contentions to year, month and date to make LocalDate example. This class gives over-burden technique to now() where we can pass ZoneId for getting date in explicit time zone. This class gives indistinguishable usefulness from java.sql.Date. How about we take a gander at a straightforward case for it's usage.

      bundle com.journaldev.java8.time; 
      import java.time.LocalDate; 
      import java.time.Month; 
      import java.time.ZoneId; 
      * LocalDate Examples 
      * @author pankaj 
      public class LocalDateExample { 
      public static void main(String[] args) { 
      //Current Date 
      LocalDate today = LocalDate.now(); 
      System.out.println("Current Date="+today); 
      //Creating LocalDate by giving information arguments 
      LocalDate firstDay_2014 = LocalDate.of(2014, Month.JANUARY, 1); 
      System.out.println("Specific Date="+firstDay_2014); 
      //Try making date by giving invalid inputs 
      //LocalDate feb29_2014 = LocalDate.of(2014, Month.FEBRUARY, 29); 
      //Exception in string "principle" java.time.DateTimeException:  
      //Invalid date 'February 29' as '2014' isn't a jump year 
      //Current date in "Asia/Kolkata", you can get it from ZoneId javadoc 
      LocalDate todayKolkata = LocalDate.now(ZoneId.of("Asia/Kolkata")); 
      System.out.println("Current Date in IST="+todayKolkata); 
      //java.time.zone.ZoneRulesException: Unknown time-zone ID: IST 
      //LocalDate todayIST = LocalDate.now(ZoneId.of("IST")); 
      //Getting date from the base date i.e 01/01/1970 
      LocalDate dateFromBase = LocalDate.ofEpochDay(365); 
      System.out.println("365th day from base date= "+dateFromBase); 
      LocalDate hundredDay2014 = LocalDate.ofYearDay(2014, 100); 
      System.out.println("100th day of 2014="+hundredDay2014); 

      LocalDate strategies clarification is given in remarks, when we run this program, we get following output.

      Current Date=2014-04-28 
      Explicit Date=2014-01-01 
      Current Date in IST=2014-04-29 
      365th day from base date= 1971-01-01 
      100th day of 2014=2014-04-10 
    2. LocalTime

      LocalTime is an unchanging class whose occurrence speaks to a period in the intelligible configuration. It's default group is hh:mm:ss.zzz. Much the same as LocalDate, this class gives time zone support and making example by passing hour, moment and second as info contentions. We should take a gander at it's utilization with a straightforward program.

      bundle com.journaldev.java8.time; 
      import java.time.LocalTime; 
      import java.time.ZoneId; 
      * LocalTime Examples 
      * @author pankaj 
      public class LocalTimeExample { 
      public static void main(String[] args) { 
      //Current Time 
      LocalTime time = LocalTime.now(); 
      System.out.println("Current Time="+time); 
      //Creating LocalTime by giving info arguments 
      LocalTime specificTime = LocalTime.of(12,20,25,40); 
      System.out.println("Specific Time of Day="+specificTime); 
      //Try making time by giving invalid inputs 
      //LocalTime invalidTime = LocalTime.of(25,20); 
      //Exception in string "principle" java.time.DateTimeException:  
      //Invalid an incentive for HourOfDay (legitimate qualities 0 - 23): 25 
      //Current date in "Asia/Kolkata", you can get it from ZoneId javadoc 
      LocalTime timeKolkata = LocalTime.now(ZoneId.of("Asia/Kolkata")); 
      System.out.println("Current Time in IST="+timeKolkata); 
      //java.time.zone.ZoneRulesException: Unknown time-zone ID: IST 
      //LocalTime todayIST = LocalTime.now(ZoneId.of("IST")); 
      //Getting date from the base date i.e 01/01/1970 
      LocalTime specificSecondTime = LocalTime.ofSecondOfDay(10000); 
      System.out.println("10000th second time= "+specificSecondTime); 

      When we keep running above program for LocalTime models, we get following output.

      Current Time=15:51:45.240 Explicit Time of Day=12:20:25.000000040 Current Time in IST=04:21:45.276 10000th second time= 02:46:40
    3. LocalDateTime

      LocalDateTime is a changeless date-time object that speaks to a date-time, with default position as yyyy-MM-dd-HH-mm-ss.zzz. It gives a manufacturing plant technique that takes LocalDate and LocalTime input contentions to make LocalDateTime example. We should look it's use with a basic example.

      package com.journaldev.java8.time; import java.time.LocalDate; import java.time.LocalDateTime; import java.time.LocalTime; import java.time.Month; import java.time.ZoneId; import java.time.ZoneOffset; public class LocalDateTimeExample { public static void main(String[] args) { //Current Date LocalDateTime today = LocalDateTime.now(); System.out.println("Current DateTime="+today); //Current Date utilizing LocalDate and LocalTime today = LocalDateTime.of(LocalDate.now(), LocalTime.now()); System.out.println("Current DateTime="+today); //Creating LocalDateTime by giving information arguments LocalDateTime specificDate = LocalDateTime.of(2014, Month.JANUARY, 1, 10, 10, 30); System.out.println("Specific Date="+specificDate); //Try making date by giving invalid inputs //LocalDateTime feb29_2014 = LocalDateTime.of(2014, Month.FEBRUARY, 28, 25,1,1); //Exception in string "principle" java.time.DateTimeException: //Invalid an incentive for HourOfDay (substantial qualities 0 - 23): 25 //Current date in "Asia/Kolkata", you can get it from ZoneId javadoc LocalDateTime todayKolkata = LocalDateTime.now(ZoneId.of("Asia/Kolkata")); System.out.println("Current Date in IST="+todayKolkata); //java.time.zone.ZoneRulesException: Unknown time-zone ID: IST //LocalDateTime todayIST = LocalDateTime.now(ZoneId.of("IST")); //Getting date from the base date i.e 01/01/1970 LocalDateTime dateFromBase = LocalDateTime.ofEpochSecond(10000, 0, ZoneOffset.UTC); System.out.println("10000th second time from 01/01/1970= "+dateFromBase); } }

      In all the three precedents, we have seen that in the event that we give invalid contentions to making Date/Time, at that point it tosses java.time.DateTimeException that is a RuntimeException, so we don't have to expressly get it.

      We have additionally observed that we can get Date/Time information by passing ZoneId, you can get the rundown of bolstered ZoneId values from it's javadoc. When we keep running above class, we get following output.

      Current DateTime=2014-04-28T16:00:49.455 
      Current DateTime=2014-04-28T16:00:49.493 
      Explicit Date=2014-01-01T10:10:30 
      Current Date in IST=2014-04-29T04:30:49.493 
      10000th second time from 01/01/1970= 1970-01-01T02:46:40 
    4. Instant

      Instant class is utilized to work with machine discernible time design, it stores date time in unix timestamp. We should see it's use with a straightforward program.

      bundle com.journaldev.java8.time; 
      import java.time.Duration; 
      import java.time.Instant; 
      public class InstantExample { 
      public static void main(String[] args) { 
      //Current timestamp 
      Moment timestamp = Instant.now(); 
      System.out.println("Current Timestamp = "+timestamp); 
      //Instant from timestamp 
      Moment specificTime = Instant.ofEpochMilli(timestamp.toEpochMilli()); 
      System.out.println("Specific Time = "+specificTime); 
      //Duration example 
      Term thirtyDay = Duration.ofDays(30); 

      Output of above program is:

      Current Timestamp = 2014-04-28T23:20:08.489Z Explicit Time = 2014-04-28T23:20:08.489Z PT720H
    5. Java 8 Date API Utilities

      As referenced before, a large portion of the Date Time guideline classes give different utility techniques, for example, in addition to/less days, weeks, months and so on. There are some other utility techniques for altering the date utilizing TemporalAdjuster and to ascertain the period between two dates.

      bundle com.journaldev.java8.time; 
      import java.time.LocalDate; 
      import java.time.LocalTime; 
      import java.time.Period; 
      import java.time.temporal.TemporalAdjusters; 
      public class DateAPIUtilities { 
      public static void main(String[] args) { 
      LocalDate today = LocalDate.now(); 
      //Get the Year, check if it's jump year 
      System.out.println("Year "+today.getYear()+" is Leap Year? "+today.isLeapYear()); 
      //Compare two LocalDate for previously and after 
      System.out.println("Today is before 01/01/2015? "+today.isBefore(LocalDate.of(2015,1,1))); 
      //Create LocalDateTime from LocalDate 
      System.out.println("Current Time="+today.atTime(LocalTime.now())); 
      //in addition to and less operations 
      System.out.println("10 days after today will be "+today.plusDays(10)); 
      System.out.println("3 weeks after today will be "+today.plusWeeks(3)); 
      System.out.println("20 months after today will be "+today.plusMonths(20)); 
      System.out.println("10 days before today will be "+today.minusDays(10)); 
      System.out.println("3 weeks before today will be "+today.minusWeeks(3)); 
      System.out.println("20 months before today will be "+today.minusMonths(20)); 
      //Temporal agents for altering the dates 
      System.out.println("First date of this month= "+today.with(TemporalAdjusters.firstDayOfMonth())); 
      LocalDate lastDayOfYear = today.with(TemporalAdjusters.lastDayOfYear()); 
      System.out.println("Last date of this year= "+lastDayOfYear); 
      Period = today.until(lastDayOfYear); 
      System.out.println("Period Format= "+period); 
      System.out.println("Months staying in the year= "+period.getMonths()); 

      Output of above program is:

      Year 2014 is Leap Year? false 
      Today is before 01/01/2015? true 
      Current Time=2014-04-28T16:23:53.154 
      10 days after today will be 2014-05-08 
      3 weeks after today will be 2014-05-19 
      20 months after today will be 2015-12-28 
      10 days before today will be 2014-04-18 
      3 weeks before today will be 2014-04-07 
      20 months before today will be 2012-08-28 
      First date of this month= 2014-04-01 
      Last date of this year= 2014-12-31 
      Period Format= P8M3D 
      Months remaining in the year= 8 
    6. Java 8 Date Parsing and Formatting

      It's extremely basic to arrange date into various organizations and afterward parse a String to get the Date Time objects. How about we see it with straightforward examples.

      bundle com.journaldev.java8.time; 
      import java.time.Instant; 
      import java.time.LocalDate; 
      import java.time.LocalDateTime; 
      import java.time.format.DateTimeFormatter; 
      public class DateParseFormatExample { 
      public static void main(String[] args) { 
      //Format examples 
      LocalDate date = LocalDate.now(); 
      //default format 
      System.out.println("Default organization of LocalDate="+date); 
      //explicit format 
      LocalDateTime dateTime = LocalDateTime.now(); 
      //default format 
      System.out.println("Default configuration of LocalDateTime="+dateTime); 
      //explicit format 
      System.out.println(dateTime.format(DateTimeFormatter.ofPattern("d::MMM::uuuu HH::mm::ss"))); 
      Moment timestamp = Instant.now(); 
      //default format 
      System.out.println("Default arrangement of Instant="+timestamp); 
      //Parse examples 
      LocalDateTime dt = LocalDateTime.parse("27::Apr::2014 21::39::48", 
      DateTimeFormatter.ofPattern("d::MMM::uuuu HH::mm::ss")); 
      System.out.println("Default design subsequent to parsing = "+dt); 

      When we keep running above program, we get following output.

      Default organization of LocalDate=2014-04-28 
      Default organization of LocalDateTime=2014-04-28T16:25:49.341 
      28::Apr::2014 16::25::49 
      Default configuration of Instant=2014-04-28T23:25:49.342Z 
      Default group subsequent to parsing = 2014-04-27T21:39:48 
    7. Java 8 Date API Legacy Date Time Support

      Legacy Date/Time classes are utilized in practically every one of the applications, so having in reverse similarity is an absolute necessity. That is the reason there are a few utility strategies through which we can change over Legacy classes to new classes and the other way around. How about we see this with a basic example.

      bundle com.journaldev.java8.time; 
      import java.time.Instant; 
      import java.time.LocalDateTime; 
      import java.time.ZoneId; 
      import java.time.ZonedDateTime; 
      import java.util.Calendar; 
      import java.util.Date; 
      import java.util.GregorianCalendar; 
      import java.util.TimeZone; 
      public class DateAPILegacySupport {
      public static void main(String[] args) { 
      //Date to Instant 
      Moment timestamp = new Date().toInstant(); 
      //Now we can change over Instant to LocalDateTime or other comparable classes 
      LocalDateTime date = LocalDateTime.ofInstant(timestamp, 
      System.out.println("Date = "+date); 
      //Calendar to Instant 
      Moment time = Calendar.getInstance().toInstant(); 
      //TimeZone to ZoneId 
      ZoneId defaultZone = TimeZone.getDefault().toZoneId(); 
      //ZonedDateTime from explicit Calendar 
      ZonedDateTime gregorianCalendarDateTime = new GregorianCalendar().toZonedDateTime(); 
      //Date API to Legacy classes 
      Date dt = Date.from(Instant.now()); 
      TimeZone tz = TimeZone.getTimeZone(defaultZone); 
      GregorianCalendar gc = GregorianCalendar.from(gregorianCalendarDateTime); 

      When we keep running above application, we get following output.

      Date = 2014-04-28T16:28:54.340 
      Mon Apr 28 16:28:54 PDT 2014 

      As you can see that inheritance TimeZone and GregorianCalendar classes toString() techniques are excessively verbose and not easy to use.

    That's totally supportive of Java 8 Date Time API, I like this new API a ton. The absolute most utilized classes will be LocalDate and LocalDateTime for this new API. It's extremely simple to work with and having comparable techniques that completes a specific occupation makes it simple to discover. It will require some investment from moving inheritance classes to new Date Time classes, yet I trust it will be deserving of the time.

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