Q:

Locale.getDefault() returns en always

Servers on unix machine are always using en as default locale.
Following is locale output
 LANG=en_US
 LC_CTYPE="C"
 LC_NUMERIC="C"
 LC_TIME="C"
 LC_COLLATE="C"
 LC_MONETARY="C"
 LC_MESSAGES="C"
 LC_ALL=C

I just don't understand if LANG is set correctly then why servers starts with en locale.

A:

In Linux/Unix/Mac, the settings LC_ALL and LANG can control the default locale for Java programs. In Windows, the locales are set from the Control Panel, under Regional and Language Options.
When the JVM starts in a *nix environment, it will do this:

Scan the environment for LC_ALL
If LC_ALL doesn't exist, scan the environment for LANG
If the JVM setting user.language is set, use that in place of the environment variables.
If nothing is set, default to en_US (I believe this is the final failure case)

In your environment, you have LC_ALL set to C, which is just the C locale. It's basically a traditional fallback to the days when locales weren't used.
You can change LC_ALL in your case, and restart your JVM, and you should get a new value for java.util.Locale.getDefault().
Example:
import java.util.Locale;

public class LocaleTest {
   public static void main(String[] args) {
      System.out.println(Locale.getDefault());
   }
}

Here's running:
> LC_ALL=en_UK java LocaleTest
en_UK

> LC_ALL=ja_JP java LocaleTest
ja_JP

Also note that if you're running Java 1.7.0-b147, there is a bug with the JRE not recognizing environment settings for locale, and will always use the default system locale.
Bug report here: http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=7073906

