Mensagem de erro "java.lang.NullPointerException"

import java.sql.Connection;

import java.sql.ResultSet;

import java.sql.Statement;

import java.sql.Connection;

import <a href="http://java.io">java.io</a>.<em>;

import <a href="http://java.net">java.net</a>.</em>;

import java.sql.SQLException;

import java.sql.ResultSet.<em>;

import java.sql.</em>;

import java.awt.event.<em>;

import java.awt.</em>;

import java.sql.SQLData.<em>;

import java.util.</em>;

import java.util.Vector;

import javax.swing.*;

import Work_ADMIN.Metodo;

public class Frm_Tabela2 extends javax.swing.JFrame

{

private String URL;

private Connection con;

public ResultSet res;

public Statement st;

public ResultSetMetaData rsmd;

public JButton jButton1;
public JButton jButton2;
public JButton jButton3;
public JLabel jLabel1;
public JTable jTable1;
public JTextField jTextField1;
public JScrollPane jScrollPane1;

Metodo metodo;

public Frm_Tabela2()
{
    setSize(800,500);
    setLocationRelativeTo(null);
   
    jLabel1 = new JLabel();
    jButton2 = new JButton();
    jTextField1 = new JTextField();
    jButton3 = new JButton();

    /*
     *-------------------------------------------------------------------------------- 
     *PAINEL panelTopo
     */
    
    JPanel painelTopo = new JPanel();
    painelTopo.setLayout(new FlowLayout(FlowLayout.LEFT));
    painelTopo.setLayout(null);
    painelTopo.setSize(800,60);

    jLabel1.setText("Localizar");
    jLabel1.setBounds(10,10,60,25);
    jTextField1.setBounds(90,10,550,25);

    jButton1 = new JButton("Localizar");
    jButton1.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
    
            String SELECT = "SELECT NOM_USUARIO FROM TESTE";
          
            conectar(); 
            buscaDados(SELECT);
           
        }
    });
    jButton1.setBounds(660,10,100,25);
     
    painelTopo.add(jLabel1);
    painelTopo.add(jTextField1);
    painelTopo.add(jButton1);
    
/*
 *---------------------------------------------------------------------------
 *PAINEL painelCentro
 */ 
     JPanel painelCentro = new JPanel();
     painelCentro.setLayout(null);
  
    conectar();
    String SELECT = "SELECT ENDERECO FROM TESTE";
    
    
    buscaDados(SELECT);
             
     jScrollPane1 = new JScrollPane();
     jScrollPane1.setBounds(10, 80, 750, 280);
     
     jScrollPane1.setViewportView(jTable1);
     painelCentro.add(jScrollPane1);
    
 /*
  *---------------------------------------------------------------------------
  *Painel panelBaixo
  */
    JPanel painelBaixo = new JPanel();
    painelBaixo.setSize(800,60);
   
    painelBaixo.setLayout(new FlowLayout(FlowLayout.RIGHT));
    
    jButton2.setText("Cadastro Novo");
    jButton3.setText("      Voltar     ");
    
    painelBaixo.add(jButton2);
    painelBaixo.add(jButton3);
    
 /*
 *--------------------------------------------------------------------------------
  */

    Container painelPrincipal = getContentPane();
    painelPrincipal.setLayout(new    BorderLayout());
    
    painelPrincipal.add(painelTopo );
    painelPrincipal.add(painelCentro);
    painelPrincipal.add(painelBaixo,  BorderLayout.SOUTH);
}

/*
 *Metodo para buscar os dados da tabelas e passar para o JTable
 */

 public void buscaDados(String SELECT)
{
    Vector cabecalho;
    Vector linhas;
    

    String SQL = SELECT;
    
    cabecalho  = new Vector();
    linhas     = new Vector();
 
    String ccol1  = "1";

                          
    try
    {
        res        = st.executeQuery(SQL);
        res.next();
        rsmd       = res.getMetaData();
        cabecalho.addElement( ccol1 );
 
        do
        {
            linhas.addElement(proximaLinha(res, rsmd));
        }
        while(res.next());
               
        jTable1 = new JTable(linhas,cabecalho);
        
       
        jScrollPane1.setViewportView(jTable1);
        validate();
        st.close();
    }
    catch(Throwable ex)
    {
        ex.printStackTrace();
    }
}

private Vector proximaLinha(ResultSet rs , ResultSetMetaData rsmd)
{
    Vector linhaAtual = new Vector();

    try
    {
        int     i;
        for(i=1; i<=rsmd.getColumnCount(); ++i)
            switch(rsmd.getColumnType( i ))
            {
                case Types.VARCHAR:
                    linhaAtual.addElement(rs.getString( i )); break;

                case Types.TIMESTAMP:
                     linhaAtual.addElement(rs.getDate( i )); break;
            }
     }       
     catch(Throwable ex) {}
     return linhaAtual;
}
public static void main(String args[]) {
    java.awt.EventQueue.invokeLater(new Runnable() {
        public void run() {
            new Frm_Tabela().setVisible(true);
        }
    });
}

public void conectar()
{
    try
    {
        Class.forName("oracle.jdbc.driver.OracleDriver");
        URL = "jdbc:oracle:thin:HDC/HDC@localhost:1521:OLTP";
        con = DriverManager.getConnection(URL);
        st  = con.createStatement();   
    }
    catch(Throwable ex)
    {
        ex.printStackTrace();
    }
}

buscaDados(SELECT); 

jScrollPane1 = new JScrollPane(); 
jScrollPane1.setBounds(10, 80, 750, 280); 

jScrollPane1.setViewportView(jTable1); 
painelCentro.add(jScrollPane1);

jScrollPane1 = new JScrollPane(); 
jScrollPane1.setBounds(10, 80, 750, 280); 
buscaDados(SELECT);
//jScrollPane1.setViewportView(jTable1); (este aqui pode ser retirado)
painelCentro.add(jScrollPane1);