Basic crawler accepts a single starting URL and total length of crawl int

Crawler.java

import java.util.ArrayList;
import java.util.HashSet;
import java.util.HashSet.*;
import org.jsoup.Jsoup;
import org.jsoup.nodes.Document;
import org.jsoup.nodes.Element;
import org.jsoup.select.Elements;
import java.io.IOException;

public class Crawler 
{
	// extracts the links from a URL, puts them in a HashSet and then returns it
	static HashSet<String>  links (String url)
	{
		HashSet<String> a = new HashSet<String>();
		try{
			org.jsoup.Connection z=Jsoup.connect(url);
	    		Document doc = z.get();
		   	Elements links = doc.select("a[href]");
	        	for (Element link : links) a.add(link.attr("abs:href"));
		   
		}
		catch (Exception e)
		{
			System.out.println(e);
		}
		return a;  
	}

	static  void Spider (String url, int n)
	{
		  HashSet<String> alreadyVisited = new HashSet <String> ();
	      	  HashSet<String> toVisit = new HashSet <String> ();
		  toVisit.addAll(links(url));
		  alreadyVisited.add(url);  
		  int i=0;
		  while (i<n && !toVisit.isEmpty())
		  {
		  	
			String z= toVisit.iterator().next();
		    	boolean already=alreadyVisited.contains(z);
			if (already) toVisit.remove(z);
			else
			{
			  System.out.println(z);
			  HashSet <String> k= links(z);
			  toVisit.addAll(k);
			  alreadyVisited.add(z);
			  System.out.printf("observed: %d visited: %d \n",toVisit.size(),alreadyVisited.size());
			  i++;
			}  
		  }
	}

    	public static void main(String[] args) throws IOException 
	{
	        String url = args[0];
		Spider(url,Integer.parseInt(args[1]));           
		   
    	}
}