code: public String[] execute() throws
            IOException,
            SpotifyWebApiException {
      List<String> genres = new Gson().fromJson(
              new JsonParser()
                      .parse(getJson())
                      .getAsJsonObject()
                      .get("genres")
                      .getAsJsonArray(),
              new TypeToken<List<String>>() {
              }.getType()
      );
  
      return genres.toArray(new String[0]);
    }
docs: Get all available genre seeds.
  
  @return All available genre seeds.
  @throws IOException            In case of networking issues.
  @throws SpotifyWebApiException The Web API returned an error further specified in this exception's root cause.