Locale Setting in Android

What is the difference between开发者_如何学运维 locales ja and ja_JP in Android? Do I have to care about both?

Thanks in advance.

Here is the definition what the difference is: http://developer.android.com/reference/java/util/Locale.html

ja = japanese ja_JP = japanese as spoken in Japan

easy is if you just implement for the local ja for everyone speaking japanese no matter where they live.