java - Which format of "en_US" and "en-US" should be used in Http header request as Accept-Language? -

i tested these 2 formats , server okay both. since http header fields saying "en-us" format , local java class returning "en_us", i'm little bit confused of them use!

my partial code this:

// set accepted language             list<string> acceptedlanguages = null;             final locale defaultlocale = locale.getdefault(); // en             if (defaultlocale != null)             {                 final string defaultlang = defaultlocale.tostring(); // en_us                 if (!textutils.isempty(defaultlang))                 {                     acceptedlanguages = new arraylist<string>();                     acceptedlanguages.add(defaultlang);                      // add en fallback if applicable                     if (!httpclient.default_accepted_language_country.equals(defaultlang))                     {                         acceptedlanguages.add(httpclient.default_accepted_language_country);                     }                 }             }              string header = httpclient.getacceptlanguageheader(acceptedlanguages); // like: cz_ch;q=1.0, en_us;q=0.9             this.mhttpgetrequest.addheader(httpheaders.accept_language, header); 

getacceptlanguageheader() method adds en_us;q=0.9to string if user's device language in not en_us.

any idea appreciated. thanks.

i believe hyphen "-" accepted part of http standard, while underscore "_" rejected. see w3c http v1.1 standard, header field definitions, section 14.4 accept-language more info.

note: w3c stands world wide web consortium.