Credo fosse un problema di driver e di impostazione del server MySQL...
Ora, dopo 123213123 smanettamenti, son riuscito ad accedere al db e a creare anche la finestra di login solo che non riesco ad interrogare il db per matchare user/passwd dell'utente con quelli presenti nel db...
In parole povere, compare la finestra di login ma non accade nulla quando provo a loggare indipendentemente da quello che inserisco nei campi...
dove sbaglio? Grazie

Qui lo screen del mio db!

https://s14.postimg.org/b16xus8rl/Mysql_demo.png

codice:
import javax.swing.*; //for creating frames
    import java.awt.event.*; //for action listeners
    import java.sql.*;//for db & queries


    public class Login {
        // statement variables
            Connection con;
            Statement st;
            ResultSet rs;
            
            static final String JDBC_DRIVER = "com.mysql.jdbc.Driver";  
            static final String DB_URL = "jdbc:mysql://localhost/demo";
            
            static final String USER = "root";
            static final String PASSWD = "root";
            
        // creating frame
            JFrame f = new JFrame("User Login");
            JLabel l = new JLabel("Username");
            JLabel l1= new JLabel ("Password");
            JTextField t = new JTextField(10);
            JTextField t1 = new JTextField(10);
            JButton b = new JButton("Login");
            
        public Login()
        {
            connect();
            frame();
        }
        
        public void connect()
        {
            Connection con = null;//create object of Connection and define it null
            try //try block
            {
                //STEP 2: Register JDBC driver
                Class.forName(JDBC_DRIVER);
                
                //STEP 3: Open a connection
                System.out.println("Connecting to a selected database...");
                con = DriverManager.getConnection(DB_URL, USER, PASSWD);
                        //print on console
                System.out.println("Connected database successfully...");            
                }
            catch(SQLException se) //catch block
            {
                //Handle errors for JDBC
                se.printStackTrace();
            }
            catch(Exception e) //catch block
            {
                //Handle errors for Class.forName
                e.printStackTrace();
            }
            finally  //finally block
            {
                //finally block used to close resources
                try  //try block
                {
                    if(con!=null)//condition
                    con.close(); //close connection
                }
                catch(SQLException se)//Handle errors
                {
                    se.printStackTrace();
                }//end finally try
            }//end try
        }
    
        public void frame()
        {
            f.setSize(500,150);
            f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            f.setVisible(true);
            
            JPanel p = new JPanel();
            p.add(l);
            p.add(t);
            p.add(l1);
            p.add(t1);
            p.add(b);
            
            f.add(p);
            
            b.addActionListener(new ActionListener() {
                public void actionPerformed (ActionEvent e)
                {
                    try
                    {
                    String user = t.getText().trim();
                    String passwd = t1.getText().trim();
                    
                    String sql = "select username, password from demo.loginaccount where username = '"+user+"'and password = '"+passwd+"'";
                    rs = st.executeQuery(sql);
                    
                    int count = 0;
                    while(rs.next())
                    {
                        count = count + 1;
                    }
                    
                    if(count == 1)
                    {
                        JOptionPane.showMessageDialog(null, "User trovato!");
                    }
                    else if(count > 1) 
                    {
                        JOptionPane.showMessageDialog(null, "Doppio User, Accesso non concesso");
                    }
                    else
                    {
                        JOptionPane.showMessageDialog(null, "User non trovato!");
                    }
                    }
                    
                    
                    catch(Exception ex)
                    {
                        
                    }
                    
                }
            });
            
            
                
        }
        
                
    
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        new Login();
        
    }


}