java.util.DateFormat - Formatting Date Objects to Strings

JDK Tutorials - Herong's Tutorial Examples

∟Date and Time Object and String Conversion

∟java.util.DateFormat - Formatting Date Objects to Strings

This section provides a tutorial example on how to use java.util.DateFormat and java.util.SimpleDateFormat classes to convert or format data objects into text strings in a specific calendar in various locales.

In the previous chapter, we learned how to use java.util.Date, java.util.Calendar and related classes to manage date, time and calendar information as objects or numeric values. If you want to convert or format date, time and calendar information into text strings in different human languages and styles, you need to learn 2 more JDK classes.

The DateFormat class, java.text.DateFormat, is an abstract class providing a foundation for subclasses to present date objects in a specific calendar in text strings, and parsing text string back to date objects.

The SimpleDateFormat class, java.text.SimpleDateFormat, is concrete subclass of the DateFormat class. It can be customized with different formatting patterns and in different locales.

Once a DateFormat object is created with a predefined pattern or a customized pattern, it can be used to convert a Date object into a string based on the pattern using the format() method. The following program shows how to create DateFormat objects and how to use them:

/* DateFormatTest.java
 * Copyright (c) HerongYang.com. All Rights Reserved.
 */
import java.util.*;
import java.text.*;
class DateFormatTest {
   public static void main(String[] a) {
      showDateFormat();
      showSimpleDateFormat();
   }
   public static void showDateFormat() {
      Date now = new Date(); // the current time
      System.out.println("Date toString() format: " + now.toString());
      DateFormat df = DateFormat.getInstance();
      System.out.println("Default DateFormat: " + df.format(now));
      df.setTimeZone(TimeZone.getTimeZone("America/Los_Angeles"));
      System.out.println("Default DateFormat in west coast: "
         + df.format(now));
      df = DateFormat.getDateTimeInstance(DateFormat.SHORT,
         DateFormat.SHORT, Locale.US);
      System.out.println("Short date time in US: " + df.format(now));
      df = DateFormat.getDateTimeInstance(DateFormat.MEDIUM,
         DateFormat.MEDIUM, Locale.US);
      System.out.println("Medium date time in US: " + df.format(now));
      df = DateFormat.getDateTimeInstance(DateFormat.SHORT,
         DateFormat.SHORT, Locale.FRENCH);
      System.out.println("Short date time in French: "
         + df.format(now));
      df = DateFormat.getDateTimeInstance(DateFormat.LONG,
         DateFormat.LONG, Locale.FRENCH);
      System.out.println("Long date time in French: "+df.format(now));
   }
   public static void showSimpleDateFormat() {
      Date now = new Date(); // the current time
      System.out.println("Date toString() format: " + now.toString());
      SimpleDateFormat sdf = new SimpleDateFormat();
      System.out.println("Default SimpleDateFormat: "
         + sdf.format(now));
      sdf = new SimpleDateFormat("dd-MMM-yyyy");
      System.out.println("The FDA standard format: "+sdf.format(now));
      sdf = new SimpleDateFormat("EEE MMM dd HH:mm:ss zzz yyyy");
      System.out.println("Date.toString() format: " +sdf.format(now));
      sdf = new SimpleDateFormat("EEE MMM dd HH:mm:ss zzz yyyy",
         Locale.FRENCH);
      System.out.println("Date.toString() format in French: "
         + sdf.format(now));
   }
}

Output:

Date toString() format: Mon Feb 19 17:37:51 ART 2024
Default DateFormat: 2/19/24, 5:37 PM
Default DateFormat in west coast: 2/19/24, 12:37 PM
Short date time in US: 2/19/24, 5:37 PM
Medium date time in US: Feb 19, 2024, 5:37:51 PM
Short date time in French: 19/02/2024 17:37
Long date time in French: 19 février 2024, 17:37:51 ART
Date toString() format: Mon Feb 19 17:37:51 ART 2024
Default SimpleDateFormat: 2/19/24, 5:37 PM
The FDA standard format: 19-Feb-2024
Date.toString() format: Mon Feb 19 17:37:51 ART 2024
Date.toString() format in French: lun. févr. 19 17:37:51 ART 2024

Note that the DateFormat class is providing predefined formats for a number of commonly used styles in different locales. The predefined formats are accessible by the get*Instance() methods.