Java functions for retrieving the genre information

youtube-genre-fonctions.java

 private static final String MUSIC_CHANNEL_ID = "UC-9-kyTW8ZkZNDHQJ6FgpwQ";
 
 /**
     * Save the genre channels information in a json file. A filtered version is also saved
     * alongside the default one. The genre playlist have to been generated for being able
     * to produce the filtered version.
     *
     * @param youtube : A {@link YouTube} for making the youtube requests
     */
    static void saveGenreChannelsInfo(YouTube youtube) throws IOException {
        //We retrieve the genre channel IDs
        final List<String> genreChannelIds = getGenreChannelIds(youtube);

        //We get the snippet for each channels IDs and save the json response in a text file
        YouTube.Channels.List channelsInfo = youtube.channels().list("snippet");
        channelsInfo.setId(StringUtils.join(genreChannelIds, ','));
        ChannelListResponse channelListResponse = channelsInfo.execute();

        //We save the default result in a json file
        String genreResponseJson = gson.toJson(channelListResponse);
        FileWriter writer = new FileWriter(OUTPUT_DIR + GENRE_DIR + "/" + GENRE_INFORMATION_FILE_NAME);
        writer.write(genreResponseJson);

        //Filtering
        List<Channel> channelList = channelListResponse.getItems().stream()
                .map(c -> changeChannelThumbnail(c, getFirstVideoIdForGenre(c.getId())))
                .collect(Collectors.toList());

        //We save the filtered result
        writer = new FileWriter(OUTPUT_DIR + GENRE_DIR + "/" + GENRE_INFORMATION_FILTER_FILE_NAME);
        writer.write(gson.toJson(channelList));
        writer.close();

    }
    
    /**
     * Retrieves all the genre channel Ids and save the list of genres in a json file
     *
     * @param youtube : A {@link YouTube} for making the youtube request
     * @return the list of genre ids
     * @throws IOException
     */
    private static List<String> getGenreChannelIds(YouTube youtube) throws IOException {
        //1 - Get the "Music genre" channel section ID
        YouTube.ChannelSections.List channelsList = youtube.channelSections().list("snippet");
        channelsList.setChannelId(MUSIC_CHANNEL_ID);
        ChannelSectionListResponse channelSectionListResponse = channelsList.execute();
        List<ChannelSection> channelSectionList = channelSectionListResponse.getItems();
        String musicGenreChannelSectionId = null;
        for (ChannelSection section : channelSectionList) {
            if (section.getSnippet().getType().equalsIgnoreCase("multipleChannels")
                    && section.getSnippet().getTitle().equalsIgnoreCase("Music Genres")) {
                musicGenreChannelSectionId = section.getId();
                break;
            }
        }

        //2 - Get the genre channels IDs (Pop Music - Topic, Hip Hop Music - Topic etc)
        YouTube.ChannelSections.List channels = youtube.channelSections().list("contentDetails");
        channels.setId(musicGenreChannelSectionId);
        channelSectionListResponse = channels.execute();
        ChannelSection musicGenreSection = channelSectionListResponse.getItems().get(0);

        return musicGenreSection.getContentDetails().getChannels();
    }