New to Java

I'm writing a fairly basic web spider which checks the validity of all the links on a given website. I wanted a class which handled parsing/connection/etc URLs, so I came up with this (incomplete due to the error I'm getting!):

import java.net.*;
import java.io.*;
import java.util.*;

public class URLHandler
{
    
    private URL url;
    private URI uri;
    
    private boolean validURLString;
    private boolean validURLConnection;
    
    private URLConnection connection;
    private BufferedReader stream;
    
    public URLHandler(String url)
    {
        String protocol;
        
        Properties systemSettings = System.getProperties();
        systemSettings.put("http.proxyHost", "");
        systemSettings.put("http.proxyPort", "");
        System.setProperties(systemSettings);
        
        if (url.indexOf("://") != -1){
            protocol = url.substring(0, url.indexOf("://"));
            url = url.substring(url.indexOf("://")+3);
        } else { // because we're dealing with websites we can assume default is http
            protocol = "http";
        }
        
        try{
            uri = new URI(protocol,url,null);
            try{
                this.url = uri.toURL();
            } catch (MalformedURLException e) {
                validURLString=false;
            } finally {
                validURLString=true;
            }
        } catch (URISyntaxException e) {
            validURLString=false;
        }

    }

    public boolean connectToURL()
    {
        System.out.println(url.getPath());
        try{
            connection = this.url.openConnection();
            connection.connect();
            stream = new BufferedReader( new InputStreamReader (connection.getInputStream()) );
        } catch (IOException e){
            validURLConnection = false;
        } finally {
            validURLConnection = true;
        }
        
        return validURLConnection;
        
    }
    
    public void write() throws IOException
    {
        String inputLine;
        while ((inputLine = stream.readLine()) != null)
            System.out.println(inputLine);
	    stream.close();

    }
    
}

I've removed the proxy settings, but I do need them as I'm behind my university's firewall. Anyway, when I invoke the connectToURL() method I just get a null pointer exception, and I'm not sure why.

Any help would be greatly appreciated!

Pete

Edited by: Puffy on Nov 13, 2007 9:08 AM