ragazzi ho fatto il seguente codice senza nessun errore:

codice:
/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */

/*
 * NumberAdditionUI.java
 *
 * Created on 29-gen-2009, 16.39.39
 */

package my.numeraddition;
import javax.swing.*;
import sun.net.ftp.*;
import sun.net.TelnetOutputStream;
import java.io.File;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.FileInputStream;



/**
 *
 * @author corradocacciapuoti
 */
public class NumberAdditionUI extends javax.swing.JFrame {



    /** Creates new form NumberAdditionUI */
    public NumberAdditionUI() {
        initComponents();
    }

    /** This method is called from within the constructor to
     * initialize the form.
     * WARNING: Do NOT modify this code. The content of this method is
     * always regenerated by the Form Editor.
     */
    @SuppressWarnings("unchecked")

    // <editor-fold defaultstate="collapsed" desc="Generated Code">                          
    private void initComponents() {

        jTabbedPane1 = new javax.swing.JTabbedPane();
        jButton3 = new javax.swing.JButton();
        jTextField1 = new javax.swing.JTextField();
        jButton1 = new javax.swing.JButton();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

        jButton3.setText("Scegli il file...");
        jButton3.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jButton3ActionPerformed(evt);
            }
        });

        jTextField1.setEditable(false);

        jButton1.setText("Upload");
        jButton1.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jButton1ActionPerformed(evt);
            }
        });

        org.jdesktop.layout.GroupLayout layout = new org.jdesktop.layout.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
            .add(org.jdesktop.layout.GroupLayout.TRAILING, layout.createSequentialGroup()
                .addContainerGap(35, Short.MAX_VALUE)
                .add(jTextField1, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE, 136, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE)
                .add(18, 18, 18)
                .add(jButton3)
                .add(49, 49, 49))
            .add(layout.createSequentialGroup()
                .add(144, 144, 144)
                .add(jButton1)
                .addContainerGap(135, Short.MAX_VALUE))
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
            .add(layout.createSequentialGroup()
                .add(39, 39, 39)
                .add(layout.createParallelGroup(org.jdesktop.layout.GroupLayout.BASELINE)
                    .add(jButton3)
                    .add(jTextField1, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE, org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE))
                .add(57, 57, 57)
                .add(jButton1)
                .addContainerGap(107, Short.MAX_VALUE))
        );

        pack();
    }// </editor-fold>                        

    private void jButton3ActionPerformed(java.awt.event.ActionEvent evt) {                                         
    
       JFileChooser chooser = new JFileChooser ();
       chooser.showOpenDialog(null);
       String file=(chooser.getSelectedFile().getAbsolutePath());
       jTextField1.setText ("" + file);

    }                                        
                                  Qua inizia il codice alla pressione del bottone upload
    private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         

String server="scaricomacfile.altervista.org";
        String userName="scaricomacfile";
        String pw="xxxxxxxx";
        String fileName=jTextField1.getText();
        FtpClient ftpClient = new FtpClient();
        try {
ftpClient.openServer(server);
            ftpClient.login(userName, pw);
            ftpClient.cd("/");
            ftpClient.binary();
            TelnetOutputStream netOut = ftpClient.put(fileName);
            File file = new File(fileName);
ObjectInputStream fileIn = new ObjectInputStream(new FileInputStream(file));
            byte c[]= new byte[1000];
            int read = 0;
            while ((read = fileIn.read(c)) != -1) {
                netOut.write(c, 0, read);
 }
                        fileIn.close();
            netOut.close();
            ftpClient.closeServer();
            }
        catch (Exception ex)
{

}





    }                                        


    /**
    * @param args the command line arguments
    */
    public static void main(String args[]) {
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new NumberAdditionUI().setVisible(true);
            }
        });
    }

    // Variables declaration - do not modify                     
    private javax.swing.JButton jButton1;
    private javax.swing.JButton jButton3;
    private javax.swing.JTabbedPane jTabbedPane1;
    private javax.swing.JTextField jTextField1;
    // End of variables declaration                   

}
però quando seleziono un file e clicco sul bottone upload e controllo nel sito di altervista non trovo niente.... cosa sbaglio?