public Optional<String> getString(String key) {
        Objects.requireNonNull(key, Required.KEY.toString());

        String value = this.values.get(key);
        if (StringUtils.isNotBlank(value)) {
            return Optional.of(value);
        }

        return Optional.empty();
    }
public Optional < String > getString ( String key ) { Objects . requireNonNull ( key , Required . KEY . toString ( ) ) ; String value = this . values . get ( key ) ; if ( StringUtils . isNotBlank ( value ) ) { return Optional . of ( value ) ; } return Optional . empty ( ) ; }
Retrieves an optional string value corresponding to the name of the form element

@param key The name of the form element
@return Optional of String