@Override
    public Optional<String> tryExtractFromIntentUrl(final String intentUrl) {
        return Optional.ofNullable(intentUrl)
                .map(url -> TextUtils.getMatch(
                        url,
                        this.matcherPattern,
                        true,
                        this.groupToExtract,
                        null,
                        false
                ))
                .map(this.matchTransformer::call);
    }
@param regex          A regular expression. Will select on group the capturing group
                      specified in other groupToExtract parameter.
@param groupToExtract which capturing group from regex to extract
main/src/main/java/cgeo/geocaching/connector/gc/util/SingleUrlToIdParser.java