Como criar um rastreador da web em java?

package local.example.crawler;

public interface ICrawler {
    void run();
}

package local.example.crawler;

public class CrawlerMaker {
    private ICrawler jsoupCrawler;

    public CrawlerMaker() {
        jsoupCrawler = new JsoupCrawler();
    }

    public void useJsoupCrawler() {
        jsoupCrawler.run();
    }
}

package local.example.crawler;

import java.io.File;
import java.io.IOException;
import java.util.List;

import org.jsoup.Jsoup;
import org.jsoup.nodes.Document;

import com.google.common.base.Charsets;
import com.google.common.io.Files;

public class JsoupCrawler implements ICrawler {

    private String urlListFile = Conf.getString("JsoupCrawler.urlListFile");
    private String reportFile = Conf.getString("JsoupCrawler.reportFile");

    @Override
    public void run() {
        List<String> urls = this.getUrlList();
        for (String url : urls) {
            this.scan(url);
        }
    }

    /**
     * @return List<String>
     */
    public List<String> getUrlList() {
        List<String> result = null;
        try {
            result = Files.readLines(new File(this.urlListFile), Charsets.UTF_8);
        } catch (IOException e) {
            e.printStackTrace();
        }
        return result;
    }

    /**
     * @param url
     */
    public void scan(String url) {
        Document doc = null;
        try {
            doc = Jsoup.connect(url).get();
        } catch (IOException e) {
            e.printStackTrace();
        }

        Integer size = doc.body().toString().length();
        String title = doc.title();
        String log = url + " === " + size + " === " + title + "n";

        System.out.println(log);

        try {
            Files.append(log, new File(this.reportFile), Charsets.UTF_8);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

package local.example.run;

import local.example.crawler.CrawlerMaker;

public class Run {
    public static void main(String[] args) {
        CrawlerMaker crawlerMaker = new CrawlerMaker();
        crawlerMaker.useJsoupCrawler();
    }
}