java搜索引擎爬虫，抓取url示例

import java.io.IOException;
import java.util.LinkedList;
import java.util.List;
import java.util.Queue;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import org.jsoup.Jsoup;
import org.jsoup.nodes.Document;
import org.jsoup.nodes.Element;
import org.jsoup.select.Elements;

public class Robot {

    // robot url
    private List<String> urlList;
    // cache url
    private Queue<String> urlQueue;
    // define Host
    public final static String HOST = "debugs.tk";

    // constructor
    public Robot() {
        super();
        // initialization robot's member
        setUrlList(new LinkedList<String>());
        setUrlQueue(new LinkedList<String>());
    }

    // url
    public List<String> getUrlList() {
        return urlList;
    }

    public void setUrlList(List<String> urlList) {
        this.urlList = urlList;
    }

    // cache
    public Queue<String> getUrlQueue() {
        return urlQueue;
    }

    public void setUrlQueue(Queue<String> urlQueue) {
        this.urlQueue = urlQueue;
    }

    // Legal link
    private boolean isURL(String url) {
        try {
            // judge url
            Pattern pattern = Pattern.compile("^[a-zA-z]+://[^s]*");
            Matcher matcher = pattern.matcher(url);
            if (matcher.matches()) {
                return true;
            } else {
                return false;
            }
        } catch (Exception e) {
            e.printStackTrace();
            return false;
        }
    }

    // whether the url is belong to host
    public static boolean isHost(String url) {
        return url.contains(HOST);
    }

    // travel all url
    public void traverse(String seed) {

        for (this.getUrlQueue().add(seed); !this.getUrlQueue().isEmpty();) {
            boolean flag = true;
            Document document = null;
            try {
                document = Jsoup.connect(seed).timeout(5000).get();
            } catch (IOException e) {
                e.printStackTrace();
                // whether connect success
                flag = false;
            }
            // whether connect success,then select a tag
            // add these aTag into queue
            if (flag) {
        // get url
                Elements elements = document.select("a[href]");
                for (Element e : elements) {
                    String s = e.attr("abs:href");
                    // Legal link and belong host
                    // and url not in list
                    // then add it
                    if (isURL(s) && s.contains(HOST)
                            && (!getUrlQueue().contains(s))
                            && (!getUrlList().contains(s))) {
                        this.getUrlQueue().add(s);
                    }
                }
            }
            // get head of queue
            // and set it seed
            // travel seed it again
            seed = this.getUrlQueue().poll();
            this.getUrlList().add(seed);
            // show information
            // System.out.println("SIZE:" 
            // + this.getUrlQueue().size() + "---"
            // + seed + " connect!");
        }
    }
}