private static Folder fromConfigStrict(@NonNull final String config) {
        final String[] tokens = config.split(CONFIG_SEP, -1);
        if (tokens.length != 3) {
            return null;
        }
        final FolderType type = EnumUtils.getEnum(FolderType.class, tokens[0]);
        if (type == null) {
            return null;
        }
        switch (type) {
            case DOCUMENT:
                return Folder.fromDocumentUri(Uri.parse(tokens[1]), tokens[2]);
            case FILE:
                return Folder.fromFile(UriUtils.toFile(Uri.parse(tokens[1])), tokens[2]);
            case PERSISTABLE_FOLDER:
                final PersistableFolder configFolder = EnumUtils.getEnum(PersistableFolder.class, tokens[1]);
                if (configFolder == null) {
                    return null;
                }
                return Folder.fromPersistableFolder(configFolder, tokens[2]);
            default:
                return null;
        }
    }
porses config strictly according to #toConfig
main/src/main/java/cgeo/geocaching/storage/Folder.java