@NonNull
    private static List<String> getVotableGeocodes(@NonNull final Collection<Geocache> caches) {
        final List<String> geocodes = new ArrayList<>(caches.size());
        for (final Geocache cache : caches) {
            final String geocode = cache.getGeocode();

            final IConnector connector = ConnectorFactory.getConnector(cache);

            if (StringUtils.isNotBlank(geocode) && connector instanceof IVotingCapability && ((IVotingCapability) connector).supportsVoting(cache)) {
                geocodes.add(geocode);
            }
        }
        return geocodes;
    }
Get geocodes of all the caches, which can be used with GCVote. Non-GC caches will be filtered out.
main/src/main/java/cgeo/geocaching/gcvote/GCVote.java