public class MyPlugin extends Plugin {
    private LanguageManager lang;
    
    @Override
    public void onEnable() {
        # Load LanguageManager. Either call that in onEnable or your config loading method.
        # Will automatically save and load any lang.<locale>.yml configs in the languages folder
        # Gets and saves language files to the folder "languages".
        # Default locale is "en"
        lang = new LanguageManager(this, "languages", "en");
        
        # Set the provider for the language of a certain sender
        # If null is returned then it will use the default locale
        # (This provider is the same as which is used by default)
        lang.setProvider(sender -> {
            if (sender instanceof ProxiedPlayer) {
                return ((ProxiedPlayer) sender).getLocale().getLanguage().replace('-', '_');
            }
            return null;
        });
    }
    
    /**
     * Get a message from a language config for a certain sender
     * @param sender        The sender to get the string for. (Language is based on this)
     * @param key           The language key in the config
     * @param replacements  An option array for replacements.
     *                (2n)-th will be the placeholder, (2n+1)-th the value. 
     *                Placeholders have to be surrounded by percentage signs: %placeholder%
     * @return The string from the config which matches the sender's language (or the default one) with the replacements replaced (or an error message, never null)
     */
    public String getMessage(CommandSender sender, String key, String... replacements) {
        return lang.getConfig(sender).get(key, replacements);
    }
}