Is it possible to change the current system language (Language Settings) from an Apex controller of a public facing vf page? We are creating a configuration menu on a vf page where the user can change the current default system language.

There is a drop down for languages in the vf page from where the user selects his language. I looked into LanguageLocaleKey and I was able to change the current language by querying user and setting different language.

This is sample code i created as proof of concept:

<apex:page controller="LanguageChangeTestController">
 
  Current system language : <apex:outputText value="{!currentLanguage}"/>
 
  <apex:form >
      <apex:commandButton value="Change language to Portuguese" action="{!changeLanguage}"/>
      <apex:commandButton value="Go back to US English" action="{!goBackToUSEng}"/>
  </apex:form>
 
</apex:page>

public with sharing class LanguageChangeTestController {

    public String currentLanguage {get; set;}
    
    public LanguageChangeTestController() {
        currentLanguage =  UserInfo.getLanguage();
    }
    
    public void changeLanguage() {
        //get current user
        String currentuserId = UserInfo.getUserId();
        User currentUserInfo = [select LanguageLocaleKey from User where Id = :UserInfo.getUserId()];
        currentUserInfo.LanguageLocaleKey = 'pt_BR';
        update currentUserInfo;
    }
    
    public void goBackToUSEng() {
        User currentUserInfo = [select LanguageLocaleKey from User where Id = :UserInfo.getUserId()];
        currentUserInfo.LanguageLocaleKey = 'en_US';
        update currentUserInfo;
    }
}

However I am not sure if I can access user id from the public facing vf page.

Any idea on how this will work for a public facing vf page?