problemi di path per lanciare pagina web

[melmar20]

ciao a tutti per lanciare una pagina web dalla mia applicazione java ho scritto :

    public void lanciaGuida(java.awt.event.MouseEvent evt){
        try {
            java.net.URL imgURLl = this.getClass().getResource("../HelpOnLine/Guida.html");
            BrowserControl.displayURL(imgURLl.toString());
        } catch (Exception ex) {
            Logger.getLogger(MainFrame.class.getName()).log(Level.SEVERE, null, ex);
        }
    }

la classe per la visualizzazione è invece questa :

package HelpOnLine;

import java.io.IOException;
/**
 * A simple, static class to display a URL in the system browser.
 *
 * Under Unix, the system browser is hard-coded to be 'netscape'.
 * Netscape must be in your PATH for this to work.  This has been
 * tested with the following platforms: AIX, HP-UX and Solaris.
 *
 * Under Windows, this will bring up the default browser under windows,
 * usually either Netscape or Microsoft IE.  The default browser is
 * determined by the OS.  This has been tested under Windows 95/98/NT.
 *
 * Examples:
    *  *
    * BrowserControl.displayURL("http://www.javaworld.com") *
    * BrowserControl.displayURL("file://c:\\docs\\index.html") *
    * BrowserContorl.displayURL("file:///user/joe/index.html"); *

 * * Note - you must include the url type -- either "http://" or
 * "file://".
 */
public class BrowserControl
{
    /**
     * Display a file in the system browser.  If you want to display a
     * file, you must include the absolute path name.
     *
     * @param url the file's url (the url must start with either "http://"
or
     * "file://").
     */
    public static void displayURL(String url)
    {
        boolean windows = isWindowsPlatform();
        String cmd = null;
        try
        {
            if (windows)
            {
                // cmd = 'rundll32 url.dll,FileProtocolHandler http://...'
                cmd = WIN_PATH + " " + WIN_FLAG + " " + url;
                Process p = Runtime.getRuntime().exec(cmd);
            }
            else
            {
                // Under Unix, Netscape has to be running for the "-remote"
                // command to work.  So, we try sending the command and
                // check for an exit value.  If the exit command is 0,
                // it worked, otherwise we need to start the browser.
                // cmd = 'netscape -remote openURL(http://www.javaworld.com)'
                cmd = UNIX_PATH + " " + UNIX_FLAG + "(" + url + ")";
                Process p = Runtime.getRuntime().exec(cmd);
                try
                {
                    // wait for exit code -- if it's 0, command worked,
                    // otherwise we need to start the browser up.
                    int exitCode = p.waitFor();
                    if (exitCode != 0)
                    {
                        // Command failed, start up the browser
                        // cmd = 'netscape http://www.javaworld.com'
                        cmd = UNIX_PATH + " "  + url;
                        p = Runtime.getRuntime().exec(cmd);
                    }
                }
                catch(InterruptedException x)
                {
                    System.err.println("Error bringing up browser, cmd='" +
                                       cmd + "'");
                    System.err.println("Caught: " + x);
                }
            }
        }
        catch(IOException x)
        {
            // couldn't exec browser
            System.err.println("Could not invoke browser, command=" + cmd);
            System.err.println("Caught: " + x);
        }
    }
    /**
     * Try to determine whether this application is running under Windows
     * or some other platform by examing the "os.name" property.
     *
     * @return true if this application is running under a Windows OS
     */
    public static boolean isWindowsPlatform()
    {
        String os = System.getProperty("os.name");
        if ( os != null && os.startsWith(WIN_ID))
            return true;
        else
            return false;
    }
    /**
     * Simple example.
     */
    public static void main(String[] args)
    {
        displayURL("http://www.javaworld.com");
    }
    // Used to identify the windows platform.
    private static final String WIN_ID = "Windows";
    // The default system browser under windows.
    private static final String WIN_PATH = "rundll32";
    // The flag to display a url.
    private static final String WIN_FLAG = "url.dll,FileProtocolHandler";
    // The default browser under unix.
    private static final String UNIX_PATH = "netscape";
    // The flag to display a url.
    private static final String UNIX_FLAG = "-remote openURL";
}

Quando lancio l'applicazione da Netbeans è tutto perfetto, ma quando crei il jar mi viene sollevato un errore di

GRAVE: null
java.lang.NullPointerException

non riesco a capire da cosa possa dipendere

[Pastore12]

Sai.. è un po' dura capire dove sia l'errore se di tutto lo stack trace ti tieni solo un misero NullPointerException...

Non uso il Logger di java e non ho idea di cosa restituisca. Se non sei capace di ricavarne altro, allora evita di gestire l'eccezione oppure stampa lo stackTrace dell'eccezione in console.