JDK Tutorials - Herong's Tutorial Examples

∟Java Date-Time API

∟java.time.format.DateTimeFormatter - Date-Time Strings

This section provides a tutorial example on how to use the java.time.format.DateTimeFormatter class to print date-time objects into strings, or to parse date-time string back as objects.

If you want to print date-time objects into strings, or want to parse them back as date-time objects, with precise control on how each date-time field is handled, you should follow the process below:

Here is a list of some commonly used pattern letters:

If you are tired of building your own format patterns with pattern letters, you may look at the documentation of java.time.format.DateTimeFormatter class, it also offers a a number of predefined format patterns for you to use. For example:

To test the java.time.format.DateTimeFormatter class and format patterns, I wrote the following sample program, DateTimeFormatterTest.java: 

/* DateTimeFormatterTest.java
 * Copyright (c) HerongYang.com. All Rights Reserved.
 */
import java.time.ZonedDateTime;
import java.time.format.DateTimeFormatter;
class DateTimeFormatterTest {
   public static void main(String[] a) {
      java.io.PrintStream out = System.out;
      String pattern = null;
      String text = null;
      DateTimeFormatter formatter = null;
      ZonedDateTime moment = ZonedDateTime.parse(
         "2014-04-01T09:06:03.008000007+02:00[Europe/Paris]");
      out.println("toString() = " + moment.toString());

      out.println();
      out.println("Test 1:");
      formatter = DateTimeFormatter.ISO_DATE_TIME;
      out.println("ISO_DATE_TIME" + " = " + moment.format(formatter));
      pattern = "yyyy-MM-dd'T'HH:mm:ss.nnnnnnnnnZZZZZ'['VV']'";
      formatter = DateTimeFormatter.ofPattern(pattern);
      text = moment.format(formatter);
      out.println(pattern + " = " + text);
      out.println("Parsed back: "
         + ZonedDateTime.parse(text,formatter));

      out.println();
      out.println("Test 2:");
      formatter = DateTimeFormatter.RFC_1123_DATE_TIME;
      out.println("RFC_1123_DATE_TIME" + " = "
         + moment.format(formatter));
      pattern = "EEE, d MMM yyyy HH:mm:ss Z";
      formatter = DateTimeFormatter.ofPattern(pattern);
      text = moment.format(formatter);
      out.println(pattern + " = " + text);
      out.println("Parsed back: "
         + ZonedDateTime.parse(text,formatter));
   }
}

When running DateTimeFormatterTest.java, I got the following output: 

herong> java DateTimeFormatterTest.java

toString() = 2014-04-01T09:06:03.008000007+02:00[Europe/Paris]

Test 1:
ISO_DATE_TIME = 2014-04-01T09:06:03.008000007+02:00[Europe/Paris]
yyyy-MM-dd'T'HH:mm:ss.nnnnnnnnnZZZZZ'['VV']' 
  = 2014-04-01T09:06:03.008000007+02:00[Europe/Paris]
Parsed back: 2014-04-01T09:06:03.008000007+02:00[Europe/Paris]

Test 2:
RFC_1123_DATE_TIME = Tue, 1 Apr 2014 09:06:03 +0200
EEE, d MMM yyyy HH:mm:ss Z = Tue, 1 Apr 2014 09:06:03 +0200
Parsed back: 2014-04-01T09:06:03+02:00

Table of Contents

 About This JDK Tutorial Book

 JDK (Java Development Kit)

►Java Date-Time API

 What Is Date-Time API

 java.time.Instant - Representing a Moment of Time

 java.time.Instant Usage Examples

 java.time.Instant - get(INSTANT_SECONDS) Error

 Converting java.util.Date to java.time.Instant

 java.time.ZonedDateTime - Calendar and Timezone

 java.time.ZonedDateTime Usage Examples

 Converting java.util.GregorianCalendar to java.time.ZonedDateTime

 java.time.OffsetDateTime - Calendar and UTC Offset

 java.time.OffsetDateTime Usage Examples

 java.time.LocalDateTime - Local Date and time without Timezone

 Partial Date and Time Objects and Classes

►java.time.format.DateTimeFormatter - Date-Time Strings

 java.time.Duration - Time Durations

 java.time.Duration Usage Examples

 java.time.Period - Periods in Days and Months

 java.time.Period Usage Examples

 Date, Time and Calendar Classes

 Date and Time Object and String Conversion

 Number Object and Numeric String Conversion

 Locales, Localization Methods and Resource Bundles

 Calling and Importing Classes Defined in Unnamed Packages

 HashSet, Vector, HashMap and Collection Classes

 Character Set Encoding Classes and Methods

 Character Set Encoding Maps

 Encoding Conversion Programs for Encoded Text Files

 Java Logging

 Socket Network Communication

 Datagram Network Communication

 DOM (Document Object Model) - API for XML Files

 SAX (Simple API for XML)

 DTD (Document Type Definition) - XML Validation

 XSD (XML Schema Definition) - XML Validation

 XSL (Extensible Stylesheet Language)

 Message Digest Algorithm Implementations in JDK

 Private key and Public Key Pair Generation

 PKCS#8/X.509 Private/Public Encoding Standards

 Digital Signature Algorithm and Sample Program

 "keytool" Commands and "keystore" Files

 KeyStore and Certificate Classes

 Secret Key Generation and Management

 Cipher - Encryption and Decryption

 The SSL (Secure Socket Layer) Protocol

 SSL Socket Communication Testing Programs

 SSL Client Authentication

 HTTPS (Hypertext Transfer Protocol Secure)

 Outdated Tutorials

 References

 Full Version in PDF/EPUB