Java date format class

Java format - Java date format class

Java 8 has a new Date-Time API to handle dates and times. /b10> We should use the new Java 8 Date-Time API to format and parse date time values.

If we are writing new code related to date and time, we should use the new Date-Time API.

Format the date and time using the new Java 8 Date Time API.

This section applies to old code that uses old dates and calendar classes.

Class

The Java library provides two classes to format the date:

• java.text.DateFormat
• java.text.SimpleDateFormat

DateFormat class is an abstract class and we can format the date in a predefined format using the DateFormat class.

Because it is abstract, we cannot create an DateFormat class new operator.

We have to use one of getXxxInstance() to create new instances. Xxx can be a date, date time, or time.

To format the date time value, we use the format() method DateFormat class.

The formatted text of the DateFormat class depends on two things:

• Style
• The language environment

The style of the format determines how much date-time information is included in the formatted text

The language environment determines the locale to use.

Format style

Date Format class defines five styles as constants:

• DateFormat.DEFAULT
• DateFormat.SHORT
• DateFormat.MEDIUM
• DateFormat.LONG
• DateFormat.FULL

DEFAULT format is the MEDIUM GetInstance() uses SHORT

The following table shows the same dates formatted in different styles for the U.S. locale.

Style	Format the date
DEFAULT	Mar 27, 2014
SHORT	3/27/14
MEDIUM	Mar 26, 2014
LONG	March 26, 2014
FULL	Sunday, November 2, 2014

Example

The following code shows how to Chinese Simplified default dates for the locale in a different format, France and Germany.

import java.text.DateFormat;
import java.util.Date;
import java.util.Locale;

public class Main {
  public static void main(String[] args) {
    Date today = new Date();

    // Print date in the default locale format
    Locale defaultLocale = Locale.getDefault();
    printLocaleDetails(defaultLocale);
    printDate(defaultLocale, today);

    // Print date in French format
    printLocaleDetails(Locale.FRANCE);
    printDate(Locale.FRANCE, today);

    // Print date in German format. We could also use Locale.GERMANY
    // instead of new Locale ("de", "DE").
    Locale germanLocale = new Locale("de", "DE");
    printLocaleDetails(germanLocale);
    printDate(germanLocale, today);
  }

  public static void printLocaleDetails(Locale locale) {
    String languageCode = locale.getLanguage();
    String languageName = locale.getDisplayLanguage();
    String countryCode = locale.getCountry();
    String countryName = locale.getDisplayCountry();
    // Print the locale info
    System.out.println("Language: " + languageName + "(" + languageCode + "); "
        + "Country: " + countryName + "(" + countryCode + ")");
  }

  public static void printDate(Locale locale, Date date) {
    DateFormat formatter = DateFormat.getDateInstance(DateFormat.SHORT, locale);
    String formattedDate = formatter.format(date);
    System.out.println("SHORT: " + formattedDate);

    formatter = DateFormat.getDateInstance(DateFormat.MEDIUM, locale);
    formattedDate = formatter.format(date);
    System.out.println("MEDIUM: " + formattedDate+"\n");

  }
}

The code above produces the following results.

java.util.Locale class contains constants for common language environments.

We can use Locale.getDefault() to get the system's default locale.

SimpleDateFormat class

To create a custom date format, we can use SimpleDateFormat class.

The SimpleDateFormat class is sensitive to the language environment.

Its default constructor creates a formatting program, and the default date format is the default locale.

The format() method in the SimpleDateFormat class executes the date format.

Example 2

To change the date format for subsequent formatting, you can use the applePattern() method by passing the new date format as an argument.

import java.text.SimpleDateFormat;
import java.util.Date;

public class Main {
  public static void main(String[] args) {
    SimpleDateFormat simpleFormatter = new SimpleDateFormat("dd/MM/yyyy");
    Date today = new Date();
    String formattedDate = simpleFormatter.format(today);
    System.out.println("Today is (dd/MM/yyyy):  " + formattedDate);

    simpleFormatter.applyPattern("MMMM dd, yyyy");
    formattedDate = simpleFormatter.format(today);
    System.out.println("Today is  (MMMM dd, yyyy): " + formattedDate);
  }

}

The code above produces the following results.