Question

there’s my code, it doesn’t work because shows emty table without any rows ir columns
can someone tel where is problem

public class test extends JFrame {

    private final JButton pridetiNaujaButton = new JButton();
    private final JButton pasalintiButton = new JButton();
    private final JButton redagotiButton = new JButton();
    private final JButton paieskaButton = new JButton();
    final GtFromDb baz=new GtFromDb();
    private Vector <Vector<String>> data;
    private Vector<String> header;
    private final JScrollPane scrollPane = new JScrollPane();
    private final JTable table = new JTable(data,header);
    public static void main(String args[]) {
        try {
            test frame = new test();
            frame.setVisible(true);
        } catch (Exception e) {
            e.printStackTrace();
        }

    }

    /**
     * Create the frame
     */
    public test() {
        super();
        setBounds(100, 100, 781, 412);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        try {
            jbInit();
        } catch (Throwable e) {
            e.printStackTrace();
        }


            GtFromDb db=new GtFromDb();
            try {
                data=db.getClient();
            } catch (Exception e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }           
            header=new Vector<String>();
            header.add("Imones pavadinimas");
            header.add("vardas");
            header.add("pavarde");
            header.add("salis");
            header.add("Adresas");
            header.add("telefonas");
        }


    private void jbInit() throws Exception {
        getContentPane().setLayout(null);

        getContentPane().add(pridetiNaujaButton);
        pridetiNaujaButton.setText("Prideti nauja");
        pridetiNaujaButton.setBounds(0, 0, 106, 26);

        getContentPane().add(pasalintiButton);
        pasalintiButton.setText("Pasalinti");
        pasalintiButton.setBounds(112, 0, 106, 26);

        getContentPane().add(redagotiButton);
        redagotiButton.setText("Redagoti");
        redagotiButton.setBounds(224, 0, 106, 26);

        getContentPane().add(paieskaButton);
        paieskaButton.setText("Paieska");
        paieskaButton.setBounds(336, 0, 106, 26);

        getContentPane().add(scrollPane);
        scrollPane.setBounds(10, 48, 745, 316);     
        scrollPane.setViewportView(table);

    }
    public class GtFromDb
    { Connection connect;
      Statement zadanie;
      String sql;
      ResultSet dane;
    //  Map<String,String> carmap =new HashMap<String,String>();
    //  Map<String,String> ownmap =new HashMap<String,String>();
    void DbConnection() throws SQLException
    {
        String baza="jdbc:odbc:dielektric_repair";
        try
        {
        Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
        }catch(Exception e){System.out.println("Connection error");}
        connect = DriverManager.getConnection(baza,"","");
    }
    public Vector getClient() throws Exception
    {
    Vector <Vector<String>> clientVector=new Vector<Vector<String>>();  
    try
    {DbConnection();
    PreparedStatement zadanie = connect.prepareStatement("SELECT * FROM Clients");

    dane = zadanie.executeQuery();
    while(dane.next()) {
    Vector <String> client=new Vector<String>();
     String imonesPav=dane.getString("Imones_pavadinimas");
     String vardas = dane.getString("Vardas");
     String pavarde = dane.getString("Pavarde");
     String salis = dane.getString("Salis");
     String adresas=dane.getString("Adresas");
     String telefonas = dane.getString("Telefonas");
     if (imonesPav != null) {imonesPav = imonesPav.trim();
     client.add(imonesPav);}
     if (vardas != null) {vardas = vardas.trim();
     client.add(vardas);}
     if (pavarde != null) {pavarde = pavarde.trim();
     client.add(pavarde);}
     if (salis != null) {salis =salis.trim();
     client.add(salis);}
     if (adresas != null) {adresas =adresas.trim();
     client.add(adresas);}
     if (telefonas != null) {telefonas = telefonas.trim();
     client.add(telefonas);}
    }zadanie.close();
    }catch(SQLException e){}
    return clientVector;    
    }
    }
    public JScrollPane getScrollPane() {
        return scrollPane;
    }
}

Answer 1

There are a few issues:

1) You are not adding the client objects to the clientVector. Use clientVector.add(client) to add the client after each iteration of the ResultSet.

2) You have initialised the table with null data and header variables. First, initialise the data and header variables and then the table, like this:

private final JTable table ;

public test() {
    super();
    setBounds(100, 100, 781, 412);
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    header=new Vector<String>();
    header.add("Imones pavadinimas");
    header.add("vardas");
    header.add("pavarde");
    header.add("salis");
    header.add("Adresas");
    header.add("telefonas");

    GtFromDb db=new GtFromDb();
    try {
        data=db.getClient();
    } catch (Exception e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }  
    table = new JTable(data,header);    

    try {
        jbInit();
    } catch (Throwable e) {
        e.printStackTrace();
    }
}

3) You are catching a SQLException and doing nothing with it. So if there is an error running the query, you will not know about it. Try printing out the stack trace:

try{
   ...
   dane = zadanie.executeQuery();
}catch(SQLException e) {
   e.printStackTrace();
} finally {
   zadanie.close();
}