Java 8 Date Parsing and Formatting with Examples

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1. Overview

  • The temporal-based classes in the Date-Time API provide parse methods for parsing a string that contains date and time information. These classes also provide format methods for formatting temporal-based objects for display. In both cases, the process is similar: you provide a pattern to the DateTimeFormatter to create a formatter object. This formatter is then passed to the parse or format method.
  • The parse and the format methods throw an exception if a problem occurs during the conversion process. Therefore, your parse code should catch the DateTimeParseException error and your format code should catch the DateTimeException error. For more information on exception handing, see Catching and Handling Exceptions.
The DateTimeFormatter class provides numerous predefined formatters, or you can define your own.
Let's use few of the predefined formatters in our examples. Examples of this guide are available on Github.

2. Parsing

The one-argument parse(CharSequence) method in the LocalDate class uses the ISO_LOCAL_DATE formatter. To specify a different formatter, you can use the two-argument parse(CharSequence, DateTimeFormatter) method.
The following example uses the predefined BASIC_ISO_DATE formatter, which uses the format 19590709 for July 9, 1959.
String in = ...;
LocalDate date = LocalDate.parse(in, DateTimeFormatter.BASIC_ISO_DATE);

2.1 LocalDate Class Formatting and Parsing Example

package com.ramesh.java8.datetime;

import java.time.LocalDate;

import java.time.format.DateTimeFormatter;

public class LocalDateFormat {
private static final DateTimeFormatter formatter = DateTimeFormatter.ofPattern("d/MM/yyyy");
private static final DateTimeFormatter formatter1 = DateTimeFormatter.ofPattern("d-MMM-yyyy");
private static final DateTimeFormatter formatter2 = DateTimeFormatter.ofPattern("d/MM/yyyy");
public static void main(String[] args) {
 //default format
 System.out.println("Default format of LocalDate = " + LocalDate.now());
   
 // The ISO date formatter that formats or parses a date without an
  // offset, such as '20111203'
 LocalDate date = LocalDate.now();
 
 System.out.println(date.format(DateTimeFormatter.BASIC_ISO_DATE));
 
 System.out.println(date.format(DateTimeFormatter.ISO_DATE));
 
 System.out.println(formatter.format(LocalDate.parse("16/08/2016", formatter)));
 
 System.out.println(formatter1.format(LocalDate.parse("16-Aug-2016", formatter1)));
 
 System.out.println(formatter2.format(LocalDate.parse("16/08/2016", formatter2)));
}
}
Output:
Default format of LocalDate = 2018-07-11
20180711
2018-07-11
16/08/2016
16-Aug-2016
16/08/2016

3. Formatting

The format(DateTimeFormatter) method converts a temporal-based object to a string representation using the specified format.

3.1 ZonedDateTime Class Formatting with Flight example

The following Flight example, converts an instance of  ZonedDateTime using the format "MMM d yyy hh:mm a". The date is defined in the same manner as was used for the previous parsing example, but this pattern also includes the hour, minutes, and a.m. and p.m. components.
package com.ramesh.java8.datetime;

import java.time.DateTimeException;
import java.time.LocalDateTime;
import java.time.Month;
import java.time.ZoneId;
import java.time.ZonedDateTime;
import java.time.format.DateTimeFormatter;
/*
 * This example uses ZonedDateTime to calculate the arrival time of
 * a flight that leaves from San Francisco and arrives in Tokyo.
 * The flight is 10 hours, 50 minutes long. Formatters are used to
 * print the departure and arrival times.
 */

public class FlightZoneDateTimeExample {
    public static void main(String[] args) {
        DateTimeFormatter format = DateTimeFormatter.ofPattern("MMM d yyyy  hh:mm a");

        // Leaving from San Francisco on July 20, 2013, at 7:30 p.m.
        LocalDateTime leaving = LocalDateTime.of(2013, Month.JULY, 20, 19, 30);
        ZoneId leavingZone = ZoneId.of("America/Los_Angeles"); 
        ZonedDateTime departure = ZonedDateTime.of(leaving, leavingZone);

        try {
            String out1 = departure.format(format);
            System.out.printf("LEAVING:  %s (%s)%n", out1, leavingZone);
        } catch (DateTimeException exc) {
            System.out.printf("%s can't be formatted!%n", departure);
            throw exc;
        }

        // Flight is 10 hours and 50 minutes, or 650 minutes
        ZoneId arrivingZone = ZoneId.of("Asia/Tokyo"); 
        ZonedDateTime arrival = departure.withZoneSameInstant(arrivingZone)
                                         .plusMinutes(650);

        try {
            String out2 = arrival.format(format);
            System.out.printf("ARRIVING: %s (%s)%n", out2, arrivingZone);
        } catch (DateTimeException exc) {
            System.out.printf("%s can't be formatted!%n", arrival);
            throw exc;
        }

        if (arrivingZone.getRules().isDaylightSavings(arrival.toInstant())) 
            System.out.printf("  (%s daylight saving time will be in effect.)%n",
                              arrivingZone);
        else
            System.out.printf("  (%s standard time will be in effect.)%n",
                              arrivingZone);
    }
}
Output:
LEAVING:  Jul 20 2013  07:30 PM (America/Los_Angeles)
ARRIVING: Jul 21 2013  10:20 PM (Asia/Tokyo)
  (Asia/Tokyo standard time will be in effect.)

3.2 LocalDateTime Class Formatting and Parsing Example

package com.ramesh.java8.datetime;

import java.time.Instant;

import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;

public class LocalDateTimeFormat {
 
public static void main(String[] args) {
  
  LocalDateTime dateTime = LocalDateTime.now();
  
  //default format
  System.out.println("Default format of LocalDateTime="+dateTime);
  
  //specific format
  System.out.println(dateTime.format(DateTimeFormatter.ofPattern("d::MMM::uuuu HH::mm::ss")));
  
  System.out.println(dateTime.format(DateTimeFormatter.BASIC_ISO_DATE));
  
  Instant timestamp = Instant.now();
  
  //default format
  System.out.println("Default format 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 format after parsing = "+dt);
 }
}
Output:
Default format of LocalDateTime=2018-07-11T16:24:57.130
11::Jul::2018 16::24::57
20180711
Default format of Instant=2018-07-11T10:54:57.179Z
Default format after parsing = 2014-04-27T21:39:48

5. Reference

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