@NotNull
    @ObjectiveCName("addPreferredLanguage:")
    public ConfigurationBuilder addPreferredLanguage(String language) {
        if (!preferredLanguages.contains(language)) {
            preferredLanguages.add(language);
        }
        return this;
    }
@ NotNull @ ObjectiveCName ( "addPreferredLanguage:" ) public ConfigurationBuilder addPreferredLanguage ( String language ) { if ( ! preferredLanguages . contains ( language ) ) { preferredLanguages . add ( language ) ; } return this ; }
Adding preferred language

@param language language code
@return this