jdbc and swing problem in netbeans

import java.io.*;
import java.awt.*;
import java.sql.*;
import java.util.*;
import javax.swing.*;

class JTableDatabase extends JFrame{
    ResultSet rs;
    JTableDatabase(){
    final Vector columnNames = new Vector();
    final Vector data = new Vector();
    JPanel panel=new JPanel();
    try{
    Class.forName("com.mysql.jdbc.Driver");
    Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/test", "root", "root");
    Statement st = con.createStatement();
    ResultSet rs= st.executeQuery("Select * from employee");
    ResultSetMetaData md = rs.getMetaData();
    int columns = md.getColumnCount();
    for(int i = 1; i <= columns; i++){
    columnNames.addElement(md.getColumnName(i));
    }
    while(rs.next()){
    Vector row = new Vector(columns);
    for(int i = 1; i <= columns; i++){
    row.addElement(rs.getObject(i));
    }
    data.addElement(row);
    }
   }
   catch(Exception e){}
   JTable table = new JTable(data, columnNames);
   JScrollPane scrollPane = new JScrollPane(table);
   panel.add(scrollPane);
   add(panel);
}
 public static void main(String arg[]){
    try{
    JTableDatabase frame=new JTableDatabase();
    frame.setSize(550,200);
    frame.setVisible(true);
    }
  catch(Exception e)
   {}
  }
}