@Nullable
    @WorkerThread
    public static String getGeocodeByUrl(@NonNull final OCApiConnector connector, @NonNull final String url) {
        final Parameters params = new Parameters("urls", url);
        final ObjectNode data = getRequest(connector, OkapiService.SERVICE_RESOLVE_URL, params).data;

        if (data == null) {
            return null;
        }

        return data.path("results").path(0).asText(null);
    }
extract the geocode from an URL, by using a backward mapping on the server
main/src/main/java/cgeo/geocaching/connector/oc/OkapiClient.java