Change site language programmatically

I need to change site language programmatically in Liferay and Im stuck. I thought that I can use LanguageUtil class, but I dont know how.

Is there any way, to change Liferay language programmatically? (I know I can do that in administration panel, but I need to have that feature in my code also).

Now my code looks like this:

@ResourceMapping("changeLanguageToEnglish")
public void changeLanguageToEnglish(){
        LanguageUtil langUtil = new LanguageUtil();
        //langUtil.setLanguage(language);
}

I can do this using the portal-ext.properties:

#
# Set the default locale used by Liferay. This locale is no longer set at
# the VM level. See LEP-2584.
#
user.country=US
user.language=en

Also by a hook

<hook>
     <language-properties>content/Language_en.properties</language-properties>
     <language-properties>content/Language_fa.properties</language-properties>
</hook>

And through a portlet

Change languaje portlet

Regards!