网络爬虫例子

public class Spider implements Runnable 
   {
    private ArrayList urls; //URL列表
    private HashMap indexedURLs; //已经检索过的URL列表
    private int threads ; //初始化线程数    
    public static void main(String argv[]) throws Exception 
    {
         if(argv[0] == null)
 {
           System.out.println("Missing required argument: [Sit URL]");
           return ;
         }
                Spider Spider = new Spider(argv[0]);
                Spider.go();
    }
    public Spider(String strURL) 
    {
        urls    = new ArrayList();
        threads = 10;
        urls.add(strURL);
        threadList = new ArrayList();
        indexedURLs = new HashMap();

        if (urls.size() == 0)
            throw new IllegalArgumentException("Missing required argument: -u [start url]");
        if (threads < 1)
            ("Invalid number of threads: " +
                threads);
    }
    public void go(String strURL) throws Exception