GestioneDatabase

import java.sql.*;
import java.awt.*;
import javax.swing.*;
import javax.swing.table.*;
import java.awt.event.*;
import java.io.*;
import javax.swing.table.AbstractTableModel;

public class GestioneDatabase extends JFrame implements ActionListener
{
    JPanel pMain            = new JPanel();
    JTabbedPane tabPane     = new JTabbedPane();
    JPanel PTabella         = new JPanel();
    JPanel PInserimento     = new JPanel();
    JPanel PAggiorna        = new JPanel();
    JPanel PElimina         = new JPanel();

    //Componenti TAB 1
    DefaultTableModel dtm;
    JTable table;
    String[] intestazione={"ID","Nome","Cognome","Classe"};
    String[][] dati;

    //Componenti TAB 2
    JTextField t_nome=new JTextField(20);
    JTextField t_cognome=new JTextField(20);
    JTextField t_classe=new JTextField(20);
    JButton b_inserisci=new JButton("Inserisci");

    Connection connection=null;
    Statement stm=null;
    ResultSet rs=null;
    String DRIVER="com.mysql.jdbc.Driver";
    String url="jdbc:mysql://localhost:3306/bagnulo_01";
    public GestioneDatabase()
    {
        try
        {
            Class.forName(DRIVER);
        }
        catch(java.lang.ClassNotFoundException e)
        {
            System.out.println("Driver non trovato "+e.getMessage());
        }
        try
        {
            connection= DriverManager.getConnection(url,"root","");
            stm=connection.createStatement();

            visualizza();
        }
        catch(Exception e)
        {
            System.err.println(e.getMessage());
        }

        dtm=new DefaultTableModel(dati,intestazione);
        JTable table=new JTable(dtm);
        PTabella.add(table);

        tabPane.addTab("Database", PTabella );
        tabPane.addTab("Inserimento", PInserimento );
        tabPane.addTab("Aggiorna", PAggiorna);
        tabPane.addTab("Elimina", PElimina);

        add(pMain);
        pMain.add(tabPane);

        this.setTitle("Gestione Database");
        this.pack();
        this.setVisible(true);
        this.setLocation(500,100);
    }

    public void actionPerformed(ActionEvent ev)
    {
    }

    public static void main(String arg[])
    {
        GestioneDatabase gdb= new GestioneDatabase();
    }

    public void visualizza()
    {
        try
        {
            int cont=0;
            rs=stm.executeQuery("SELECT * FROM studenti");

            while(rs.next())
            {
                String id=rs.getString(1);
                String nome=rs.getString(2);
                String cognome=rs.getString(3);
                String classe=rs.getString(4);
                System.out.println(id+nome+cognome+classe);
                dati[cont][0]=id;
                dati[cont][1]=nome;
                dati[cont][2]=cognome;
                dati[cont][3]=classe;
                cont++;
            }
        }
        catch(Exception e)
        {
            System.out.println(e.getMessage());
        }
    }
}