How do I set the default locale in the JVM?

Question

You can set it on the command line via JVM parameters:

java -Duser.country=CA -Duser.language=fr ... com.x.Main

For further information look at Internationalization: Understanding Locale in the Java Platform - Using Locale

From the Oracle Reference:

The default locale of your application is determined in three ways. First, unless you have explicitly changed the default, the Locale.getDefault() method returns the locale that was initially determined by the Java Virtual Machine (JVM) when it first loaded. That is, the JVM determines the default locale from the host environment. The host environment's locale is determined by the host operating system and the user preferences established on that system.

Second, on some Java runtime implementations, the application user can override the host's default locale by providing this information on the command line by setting the user.language, user.country, and user.variant system properties.

Third, your application can call the Locale.setDefault(Locale) method. The setDefault(Locale aLocale) method lets your application set a systemwide (actually VM-wide) resource. After you set the default locale with this method, subsequent calls to Locale.getDefault() will return the newly set locale.

You can use JVM args

java -Duser.country=ES -Duser.language=es -Duser.variant=Traditional_WIN

In the answers here, up to now, we find two ways of changing the JRE locale setting:

• Programatically, using Locale.setDefault() (which, in my case, was the solution, since I didn't want to require any action of the user):

  Locale.setDefault(new Locale("pt", "BR"));
  

• Via arguments to the JVM:

  java -jar anApp.jar -Duser.language=pt-BR
  

But, just as reference, I want to note that, on Windows, there is one more way of changing the locale used by the JRE, as documented here: changing the system-wide language.

Note: You must be logged in with an account that has Administrative Privileges.

1. Click Start > Control Panel.

2. Windows 7 and Vista: Click Clock, Language and Region > Region and Language.

   Windows XP: Double click the Regional and Language Options icon.

   The Regional and Language Options dialog box appears.

3. Windows 7: Click the Administrative tab.

   Windows XP and Vista: Click the Advanced tab.

   (If there is no Advanced tab, then you are not logged in with administrative privileges.)

4. Under the Language for non-Unicode programs section, select the desired language from the drop down menu.

5. Click OK.

   The system displays a dialog box asking whether to use existing files or to install from the operating system CD. Ensure that you have the CD ready.

6. Follow the guided instructions to install the files.

7. Restart the computer after the installation is complete.

Certainly on Linux the JRE also uses the system settings to determine which locale to use, but the instructions to set the system-wide language change from distro to distro.

There is another away if you don't like to change System locale but the JVM. you can setup a System (or user) Environment variable JAVA_TOOL_OPTIONS and set its value to -Duser.language=en-US or any other language-REGION you want.