Chapter 12 ■ Localization

Points to Remember

Here are some pointers that might prove useful on your exam:

•There are many ways to get or create a Locale object. We list four options here for creating an instance of Italian locale that corresponds to the language code of it.

Option 1: Use the constructor of the Locale class: Locale(String language, String country, String variant):

Locale locale1 = new Locale("it", "", "");

Option 2: Use the forLanguageTag(String languageTag) method in the Locale class:

Locale locale2 = Locale.forLanguageTag("it");

Option 3: Build a Locale object by instantiating Locale.Builder and then call setLanguageTag() from that object:

Locale locale3 = new Locale.Builder().setLanguageTag("it").build();

Option 4: Use the predefined static final constants for locales in the Locale class:

Locale locale4 = Locale.ITALIAN;

You can choose the way to create a Locale object based on your need. For example, the Locale class has only a few predefined constants for locales. If you want a Locale object from one of the predefined ones, you can straightaway use it, or you’ll have to check which other option to use.

•Instead of calling Locale’s getDisplayCountry() method, which takes no arguments, you can choose the overloaded version of getDisplayCountry(Locale), which takes a Locale object as an argument. This will print the name of the country as in the passed locale. For example, for the call Locale.GERMANY.getDisplayCountry(), you’ll get the output “Deutschland” (that’s how Germans refer to their country); however, for the call Locale.GERMANY. getDisplayCountry(Locale.ENGLISH), you’ll get the output “Germany” (that’s how British refer to the country name Germany).

Question Time!

1.Consider this program:

import java.text.NumberFormat; import java.text.ParseException;

public class FractionDigits {

public static void main(String[] args) {

String[] numbers = {"1.222", "0.456789F"};

NumberFormat numberFormat = NumberFormat.getInstance(); numberFormat.setMaximumFractionDigits(2);

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for(String number : numbers) { try {

System.out.println(numberFormat.parse(number));

}

catch(ParseException pe) {

System.out.println("Failed parsing " + number);

}

}

}

}

This program prints which of the following?

A)1.22

0.45

B)1.22

0.46

C)1.222

0.456789

D)1.222

Failed parsing 0.456789

E)Failed parsing 1.222 0.456789

F)Failed parsing 1.222 Failed parsing 0.456789

Answer:

C)1.222

0.456789

(The parse() method reads the values and converts it to Number if it succeeds. So, it does not use the maximum fraction digits set using setMaximumFractionDigits; however, if it were to use the format() method, which is meant for printing numbers, it will use this maximum fraction digits limit set.)

2.Consider this program:

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

import java.util.Locale;

// Use SimpleDateFormat for creating custom date and time formats as a "pattern string" class PatternStringExample {

public static void main(String []args) { String pattern = "EEEE";

SimpleDateFormat formatter = new SimpleDateFormat(pattern, Locale.US);

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Date today = new Date(); System.out.println(formatter.format(today));

}

}

Which of the following is the most likely output (i.e., the output that would match with the string pattern EEEE given in this code segment)?

A)F

B)Friday

C)Sept

D)September Answer: B)  Friday

(E is the day name in the week; the pattern EEEE prints the name of the day in its full format. Fri is a short form which would be printed by the pattern E, but EEEE will print the day of the week in full form, i.e., Friday. Since the locale is us Locale.US, it will print in English. Sept or September is impossible since E refers to the name in the week, not in a month.)

3.Which one of the following statements makes use of a factory method?

A)Locale locale1 = new Locale("it", "", "");

B)NumberFormat.getInstance(Locale.GERMANY);

C)Locale locale3 = new Locale.Builder().setLanguageTag("it").build();

D)Date today = new Date();

E)Locale locale4 = Locale.ITALIAN;

Answer: B)  NumberFormat.getInstance(Locale.GERMANY);

(A factory method creates an instance and returns back. Using a constructor directly to create an object is not related to a factory method, so A) and D) are not correct. C) builds a locale and is perhaps an example for the Builder pattern. E) merely accesses the predefined Locale object; so it’s not a method.)

4.Which of the following is a correct override for extending the ListResourceBundle class?

A)public HashMap < String, String > getContents() {

Map < String, String > contents = new HashMap<>(); contents.add("MovieName", "Avatar");

return contents;

}

B)public Object[] getContents() {

return new Object[] { { "MovieName" } , { "Avatar" } };

}

C)public Object[][] getContents() {

return new Object[][] { { "MovieName", "Avatar" } };

}

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D)public String[] getKeysAndValues() {

return new String[] { { "MovieName" } , { "Avatar" } };

}

e)public String[] getProperties() {

return new String[] { { "MovieName" }, { "Avatar" } };

}

Answer: C)

public Object[][] getContents() {

return new Object[][] { { "MovieName", "Avatar" } };

}

(the return type of the getContents() method is Object[][]. Further, the method should return a new object of type Object [][]. So C) is the correct answer.)

Summary

Read and Set the Locale Using the Locale Object

•A locale represents a language, culture, or country; the Locale class in Java provides an abstraction for this concept.

•Each locale can have three entries: the language, country, and variant. You can use standard codes available for language and country to form locale tags. There are no standard tags for variants; you can provide variant strings based on your need.

•The getter methods in the Locale class—such as getLanguage(), getCountry(), and getVariant()—return codes; whereas the similar methods of getDisplayCountry(), getDisplayLanguage(), and getDisplayVariant() return names.

•The getDefault() method in Locale returns the default locale set in the JVM. You can change this default locale to another locale by using the setDefault() method.

•There are many ways to create or get a Locale object corresponding to a locale:

•Use the constructor of the Locale class.

•Use the forLanguageTag(String languageTag) method in the Locale class.

•Build a Locale object by instantiating Locale.Builder and then call setLanguageTag() from that object.

•Use the predefined static final constants for locales in the Locale class.

Build a Resource Bundle for Each Locale

•A resource bundle is a set of classes or property files that help define a set of keys and map those keys to locale-specific values.

•The class ResourceBundle has two derived classes: PropertyResourceBundle and ListResourceBundle. You can use ResourceBundle.getBundle() to automatically load a bundle for a given locale.

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•The PropertyResourceBundle class provides support for multiple locales in the form of property files. For each locale, you specify the keys and values in a property file for that locale. You can use only Strings as keys and values.

•To add support for a new locale, you can extend the ListResourceBundle class. In this derived class, you have to override the Object [][] getContents() method. The returned array must have the list of keys and values. The keys must be Strings, and values can be any objects.

•When passing the key string to the getObject() method to fetch the matching value in the resource bundle, make sure that the passed keys and the key in the resource bundle exactly match (the keyname is case sensitive). If they don’t match, you’ll get a

MissingResourceException.

•The naming convention for a fully qualified resource bundle name is packagequalifier.bundlename + "_" + language + "_" + country + "_" + (variant + "_#" | "#") + script + "-" + extensions.

Load a Resource Bundle in an Application

•The process of finding a matching resource bundle is same for classes extended from

ListResourceBundles as for property files defined for PropertyResourceBundles.

•Here is the search sequence to look for a matching resource bundle. Search starts from Step 1. If at any step the search finds a match, the resource bundle is loaded. Otherwise, the search proceeds to the next step.

•Step 1: The search starts by looking for an exact match for the resource bundle with the full name.

•Step 2: The last component (the part separated by _) is dropped and the search is repeated with the resulting shorter name. This process is repeated till the last locale modifier is left.

•Step 3: The search is restarted using the full name of the bundle for the default locale.

•Step 4: Search for the resource bundle with just the name of the bundle.

•Step 5: The search fails, throwing a MissingBundleException.

•The getBundle() method takes a ResourceBundle.Control object as an additional parameter. By extending this ResourceBundle.Control class and passing that object, you can control or customize the resource bundle searching and loading process.

Format Text for Localization Using NumberFormat and DateFormat

•To handle date and time, numbers, and currencies in a culture-sensitive way, you can use the java.text.Format class and its two main derived classes NumberFormat and DateFormat for that.

•The NumberFormat class provides support locale-sensitive handling of numbers relating to how thousands are separated, treating a number as a currency value, etc.

•The NumberFormat class provides methods to format or parse numbers. “Formatting” means converting a numeric value to a textual form suitable for displaying to users; “parsing” means converting a number back to numeric form for use in the program. The parse() method returns a Number if successful—otherwise it throws ParseException (a checked exception).

•NumberFormat has many factory methods: getInstance(), getCurrencyInstance(), getIntegerInstance(), and getPercentInstance().

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•The Currency class provides support for handling currency values in a locale-sensitive way.

•The DateFormat class provides support for processing date and time in a locale-sensitive manner.

•The DateFormat has three overloaded factory methods—getDateInstance(), getTimeInstance(), and getDateTimeInstance()—that return DateFormat instances for processing date, time, and both date and time, respectively.

•SimpleDateFormat (derived from DateFormat) uses the concept of a pattern string to support custom formats for date and time.

•You encode the format of the date or time using case-sensitive letters to form a date or time pattern string.

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