<pre class="brush:java; toolbar: true; auto-links: false;">package se.robot;  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!");   }  }   // public static void main(String[] args) {  // Robot robot = new Robot();  // robot.traverse("http://debugs.tk");  // List<String> list = robot.getUrlList();  // for (String s : list) {  // System.out.println(s);  // }  // }  }</pre>    <br />