Java Gold Countermeasures: Localization

Introduction

This paper summarizes the following items as a summary of Java Gold learning. (Also for those who are learning Java Gold or want to know about localization.)

• Locale
• Resource bundle

What is a locale?

java.util.Locale

Show the notation rules for things that differ by language and country.

Example: Units, symbols, dates, currencies, etc.

Use the locale when you want to change the display for each country where the application is used. (Characters are divided into Japanese and English depending on the country where the app is used, etc.)

There are three main methods for creating an instance.

• new
• Local class constant
• getDefault () method

■ Main constructors and methods

//Instantiation with new
//ja ・ en: Language name code ｜ JP ・ US: Country code
Locale localeJp = new Locale("ja","JP");  //Japanese locale
Locale localeUs = new Locale("en","US");  //American locale

//Instance generation by Locale class constant
Locale localeJp = Locale.JAPAN;
Locale localeUs = Locale.US;

// getDefault()Instantiation by method
//When executed in Japan, a Japanese Locale instance is generated.
Locale localeJp = Locale.getDefault();

// ja_JP is stored (when OS is Japan)
Locale locale = Locale.getDefault();

//Japan is stored
String country = locale.getDisplayCountry();

//Japanese is stored
String language = locale.getDisplayLanguage();

//JP is stored
String country_code = locale.getCountry();

//ja is stored
String language_code = locale.getLanguage();

//Remarks: Other instantiation methods
Locale locale = new Locale.Builder().setLanguage("ja")
                                    .setScript("Jpan")
                                    .setRegion("JP")
                                    .build();
// setScript(): The argument is ISO 15924 alpha-4 Script code (see Javadoc)
// build()：Locale.Create Local object with Builder method

Resource bundle

java.util.ResourceBundle

Correspond to different notation rules for each language and country according to the locale. This makes it possible to switch between Japanese notation and English notation according to the locale.

The main methods used are as follows.

In addition, there are the following as subclasses.

■ When using ListResourceBundle

The definition rules when using this are as follows.

• Definition method

• Create a public class that inherits ListResourceBundle

• Override the getContents () method to create a list of resources in an array

• Resources are created as an array with keys and values as elements

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** ▼ Implementation example **

Resource.java

public class Resource extends ListResourceBundle {

	public Object[][] getContents() {
		Object[][] contents = {
				{"apple", "Apple"},
				{"orange", "Orange"}
		};
		return contents;
	}
}

Resource_en_US.java

public class Resource_en extends ListResourceBundle {

	protected Object[][] getContents() {
		Object[][] contents = {
				{"apple", "apple"},
				{"orange", "orange"}
		};
		return contents;
	}
}

Locale by setting base name_language code_country code.java The file of the language corresponding to the object of is referenced.

For the default locale instance, the base name resource is referenced. If only the language code is specified for the locale instance, only the language code needs to be specified after the base name.

Main.java

//The output result is as follows
//Apple:Orange
// apple:orange

class Main {
	public static void main(String[] args) {

		Locale localeJa = Locale.JAPAN;
		Locale localeUs = Locale.US;

		//If the second argument is not specified, specify the default locate.
		List<Locale> locales =
				new ArrayList<Locale>(Arrays.asList(localeJa, localeUs));

		for(Locale locale : locales) {
			//package name.Specify the file name
			ResourceBundle rb =
				ResourceBundle.getBundle("resource.Resource", locale);

			//If you want to get something other than String, cast it using the getObject method
			System.out.println(rb.getString("apple") + ":" + rb.getString("orange"));
		}
	}
}

■ When using PropertyResourceBuilder

The definition rules when using this are as follows.

• Property file name is base name_language code_country code.properties
• Resource keys and values are listed in the properties file in the form key = value

** ▼ Implementation example **

Source.properties

apple=J_apple
orange=J_orange

Source_en_US.properties

apple=U_apple
orange=U_orange

Main.java

//Output result
// J_appleJ_orange
// U_appleU_orange

class Main {
	public static void main(String[] args) throws MalformedURLException {

        File dicDir = Paths.get(".\\resource").toFile();

        URLClassLoader urlLoader;
        urlLoader = new URLClassLoader(new URL[]{dicDir.toURI().toURL()});

		Locale localeJp = Locale.JAPAN;
		Locale localeUs = Locale.US;

		List<Locale> locales =
				new ArrayList<Locale>(Arrays.asList(localeJp, localeUs));

		for (Locale locale : locales) {
			//Specify only the file name
			ResourceBundle rb =
					ResourceBundle.getBundle("Source" ,locale ,urlLoader);

			System.out.println(rb.getString("apple") + rb.getString("orange"));

		}
	}
}

References

• https://docs.oracle.com/javase/jp/7/api/java/util/Locale.html
• https://docs.oracle.com/javase/jp/8/docs/api/java/util/ResourceBundle.html