private void retrieveTest() {
        TweetManager manager = new TweetManager();
        List<Tweet> tweets = manager.retrieveAll();
        int count = 0;
        for (Tweet tweet : tweets) {
            if (!tweet.isSingleCategory())
                continue;
            //System.out.println(tweet.getCategory() + "," + tweet.getCleanText());
            count++;
        }
        System.out.println(count);
    }