Find application category on Android without dependencies by parsing the HTML from Play Store

PlayCrawler.java

import java.util.NoSuchElementException;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

// Created by Jonatan Hamberg on 11.3.2019.
// (C) 2019 - University of Helsinki

public class PlayCrawler {
    // Find an opening anchor tag "<a" followed by any number of non-closing characters (spaces
    // or attributes) preceding an itemprop for genre "itemprop=\"genre\"". Following the genre,
    // again, find any number of non-closing characters "[^>]+" preceding an href attribute
    // "href=\"" with a value prefixed with either http or https "https?://". Proceeding with
    // the value, find the Play Store url "play.google.com/store/apps/category/" and capture its
    // last non-closing segment "([^/"]+)". This capture represents the application category.
    private static final String PATTERN_CATEGORY =
            "<a itemprop=\"genre\"[^>]+" +
            "href=\"https?://play.google.com/store/apps/category/([^\"]+)\"";

    public static String parseCategory(String html) {
        Pattern pattern = Pattern.compile(PATTERN_CATEGORY);
        Matcher matcher = pattern.matcher(clean(html));
        if (matcher.find() && matcher.groupCount() > 1) {
            return matcher.group(1);
        }
        return null;
    }

    private static String clean(String html) {
        // Replace all newlines with a space and then trim all repeating whitespaces. This helps
        // with html tags that span multiple lines that might or might not have trailing spaces
        // before the newline.
        return html.replace("\n", " ")
                .replaceAll(" +", " ");
    }
}