• Localization (l10n):
  • The adaptation of a product to meet the requirements of a particular locale (including language and cultural differences)
• Internationalization (i18n):
  • The design of a product that facilitates localization

• Terminology:
  • Language Differences
• Formatting and Symbols:
  • Numbers
  • Dates and Times
  • Addresses
  • Currencies

• Encapsulation:
  • The Locale class encapsulates language (ISO 639), a script or writing system (ISO 15924), a country or region (ISO 3166), and a variant (IETF BCP47) like Canadian French or Swiss German
• Determination:
  • The JVM determines the Locale of the processor it is running on at startup (which can be retrieved using Locale.getDefault() )

• Changing from the Command Line:
  • Use the -Duser.country and -Duser.language options (e.g., java -Duser.country=CA -Duser.language=fr MainClass )
• Changing within a Program:
  • Invoke Locale.setDefault(java.util.Locale)

• On-Line:
  • Use machine translation at run-time
• Off-Line:
  • Use machine translation or human translation to create a mapping at build time

• The Important Class:
  • ResourceBundle
• Use:
  • Create a file containing a mapping between keys (in the developer's natural language) and values (in the user's natural language)
  • Load the appropriate mapping based on the Locale

Some Example Files

Strings_en_US.properties

CANCEL = Cancel
FILE = File
OPEN = Open

Strings_fr_FR.properties

CANCEL = Annuler
FILE = Fichier
OPEN = Ouvrir

Using the Files

// Declare and initialize a static attribute
public static final ResourceBundle STRINGS = 
  ResourceBundle.getBundle("calc.ui.Strings");



// Use the static attribute to create a JButton
JButton cancelButton = new JButton(STRINGS.getString("CANCEL"));
cancelButton.setActionCommand("CANCEL");


// Respond to an event
public void actionPerformed(ActionEvent evt)
{
  String command = evt.getActionCommand();
  if (ac.equals("CANCEL"))
  {
    // Respond appropriately
  }
}
  

• Some Issues:
  • The symbol between the one's place and the one-tenth's place
  • The symbol used for groupings of places
  • Formatting positive and negative numbers
• Useful Classes/Methods:
  • There are versions of printf() (in PrintStream ) and format() (in String ) that are passed a Locale and the versions that aren't passed a Locale invoke the versions that do, passing the default Locale
  • The NumberFormat class provides even more flexibility, though it is less convenient

• Some Issues:
  • The currency symbol
  • The placement of the currency symbol (before or after the amount)
  • All of the issues for numbers
• Useful Classes/Methods:
  • The NumberFormat class has a static getCurrencyInstance() class that returns a NumberFormat object that will format currency information in a locale-specific way

• Some Issues:
  • Words or numbers (especially for the month)
  • Ordering of the year, month, and day
• Useful Classes/Methods:
  • The DateFormat class has a format() method that can be used to format dates in a variety of ways (including SHORT, MEDIUM, LONG and FULL representations)

(Courtesy of xkcd)