Como resolver o erro "AWT-EventQueue-0"

Boa noite, não sei mais o que fazer para resolver esse problema… por favor se alguém puder me ajudar, ficarei muito grato!
O meu código é:

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
package Formularios;

/**
 *
 * @author Marcio
 */
import java.sql.*;
import javax.swing.JOptionPane;
import utilitarios.ConectaBanco;

public class FrmEstado extends javax.swing.JFrame {
    ConectaBanco conexao = new ConectaBanco();//instancia da classe de conexao
    
   
    public FrmEstado() {
        initComponents();
        conexao.conecta();//chama o metodo conecta
    }

    /**
     * This method is called from within the constructor to initialize the form.
     * WARNING: Do NOT modify this code. The content of this method is always
     * regenerated by the Form Editor.
     */
    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">                          
    private void initComponents() {

        jPanel1 = new javax.swing.JPanel();
        jLabel2 = new javax.swing.JLabel();
        jLabel3 = new javax.swing.JLabel();
        jLabel4 = new javax.swing.JLabel();
        jTextFieldCodigo = new javax.swing.JTextField();
        jTextFieldNome = new javax.swing.JTextField();
        jTextFieldSigla = new javax.swing.JTextField();
        jButtonNovo = new javax.swing.JButton();
        jButtonSalvar = new javax.swing.JButton();
        jButtonExcluir = new javax.swing.JButton();
        jButtonEditar = new javax.swing.JButton();
        jButtonSair = new javax.swing.JButton();
        jScrollPane1 = new javax.swing.JScrollPane();
        jTable1 = new javax.swing.JTable();
        jButtonPrimeiro = new javax.swing.JButton();
        jButtonUltimo = new javax.swing.JButton();
        jButtonAnterior = new javax.swing.JButton();
        jButtonProximo = new javax.swing.JButton();
        jLabel1 = new javax.swing.JLabel();

        setDefaultCloseOperation(javax.swing.WindowConstants.DISPOSE_ON_CLOSE);
        setTitle("Cadastro de Estados");

        jPanel1.setBorder(javax.swing.BorderFactory.createEtchedBorder());

        jLabel2.setText("Código");

        jLabel3.setText("Nome");

        jLabel4.setText("Sigla");

        jTextFieldCodigo.setDisabledTextColor(new java.awt.Color(0, 0, 0));
        jTextFieldCodigo.setEnabled(false);

        jTextFieldNome.setDisabledTextColor(new java.awt.Color(0, 0, 0));
        jTextFieldNome.setEnabled(false);
        jTextFieldNome.setName("nome"); // NOI18N

        jTextFieldSigla.setDisabledTextColor(new java.awt.Color(0, 0, 0));
        jTextFieldSigla.setEnabled(false);

        jButtonNovo.setIcon(new javax.swing.ImageIcon(getClass().getResource("/imagens/New_32x32.png"))); // NOI18N
        jButtonNovo.setToolTipText("Novo");
        jButtonNovo.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jButtonNovoActionPerformed(evt);
            }
        });

        jButtonSalvar.setIcon(new javax.swing.ImageIcon(getClass().getResource("/imagens/Save_32x32.png"))); // NOI18N
        jButtonSalvar.setToolTipText("Salvar");
        jButtonSalvar.setEnabled(false);
        jButtonSalvar.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jButtonSalvarActionPerformed(evt);
            }
        });

        jButtonExcluir.setIcon(new javax.swing.ImageIcon(getClass().getResource("/imagens/Delete_32x32.png"))); // NOI18N
        jButtonExcluir.setToolTipText("Excluir");
        jButtonExcluir.setEnabled(false);
        jButtonExcluir.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jButtonExcluirActionPerformed(evt);
            }
        });

        jButtonEditar.setIcon(new javax.swing.ImageIcon(getClass().getResource("/imagens/Edit_32x32.png"))); // NOI18N
        jButtonEditar.setToolTipText("Editar");
        jButtonEditar.setEnabled(false);
        jButtonEditar.setName("Editar"); // NOI18N
        jButtonEditar.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jButtonEditarActionPerformed(evt);
            }
        });

        jButtonSair.setIcon(new javax.swing.ImageIcon(getClass().getResource("/imagens/Log Out_32x32.png"))); // NOI18N
        jButtonSair.setToolTipText("Sair");
        jButtonSair.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jButtonSairActionPerformed(evt);
            }
        });

        jTable1.setModel(new javax.swing.table.DefaultTableModel(
            new Object [][] {
                {null, null, null, null},
                {null, null, null, null},
                {null, null, null, null},
                {null, null, null, null}
            },
            new String [] {
                "Title 1", "Title 2", "Title 3", "Title 4"
            }
        ));
        jScrollPane1.setViewportView(jTable1);

        jButtonPrimeiro.setIcon(new javax.swing.ImageIcon(getClass().getResource("/imagens/Stock Index Up_32x32.png"))); // NOI18N
        jButtonPrimeiro.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jButtonPrimeiroActionPerformed(evt);
            }
        });

        jButtonUltimo.setIcon(new javax.swing.ImageIcon(getClass().getResource("/imagens/Stock Index Down_32x32.png"))); // NOI18N
        jButtonUltimo.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jButtonUltimoActionPerformed(evt);
            }
        });

        jButtonAnterior.setIcon(new javax.swing.ImageIcon(getClass().getResource("/imagens/Previous_32x32.png"))); // NOI18N
        jButtonAnterior.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jButtonAnteriorActionPerformed(evt);
            }
        });

        jButtonProximo.setIcon(new javax.swing.ImageIcon(getClass().getResource("/imagens/Next_32x32.png"))); // NOI18N
        jButtonProximo.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jButtonProximoActionPerformed(evt);
            }
        });

        javax.swing.GroupLayout jPanel1Layout = new javax.swing.GroupLayout(jPanel1);
        jPanel1.setLayout(jPanel1Layout);
        jPanel1Layout.setHorizontalGroup(
            jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(jPanel1Layout.createSequentialGroup()
                .addContainerGap()
                .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addComponent(jScrollPane1)
                    .addGroup(jPanel1Layout.createSequentialGroup()
                        .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING, false)
                            .addGroup(javax.swing.GroupLayout.Alignment.LEADING, jPanel1Layout.createSequentialGroup()
                                .addComponent(jLabel3)
                                .addGap(18, 18, 18)
                                .addComponent(jTextFieldNome))
                            .addGroup(javax.swing.GroupLayout.Alignment.LEADING, jPanel1Layout.createSequentialGroup()
                                .addComponent(jButtonNovo, javax.swing.GroupLayout.PREFERRED_SIZE, 50, javax.swing.GroupLayout.PREFERRED_SIZE)
                                .addGap(18, 18, 18)
                                .addComponent(jButtonSalvar, javax.swing.GroupLayout.PREFERRED_SIZE, 50, javax.swing.GroupLayout.PREFERRED_SIZE)
                                .addGap(18, 18, 18)
                                .addComponent(jButtonEditar, javax.swing.GroupLayout.PREFERRED_SIZE, 50, javax.swing.GroupLayout.PREFERRED_SIZE)
                                .addGap(18, 18, 18)
                                .addComponent(jButtonExcluir, javax.swing.GroupLayout.PREFERRED_SIZE, 50, javax.swing.GroupLayout.PREFERRED_SIZE)))
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                        .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                            .addComponent(jButtonSair, javax.swing.GroupLayout.Alignment.TRAILING, javax.swing.GroupLayout.PREFERRED_SIZE, 49, javax.swing.GroupLayout.PREFERRED_SIZE)
                            .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, jPanel1Layout.createSequentialGroup()
                                .addComponent(jLabel4)
                                .addGap(18, 18, 18)
                                .addComponent(jTextFieldSigla, javax.swing.GroupLayout.PREFERRED_SIZE, 35, javax.swing.GroupLayout.PREFERRED_SIZE))))
                    .addGroup(jPanel1Layout.createSequentialGroup()
                        .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                            .addGroup(jPanel1Layout.createSequentialGroup()
                                .addComponent(jLabel2)
                                .addGap(18, 18, 18)
                                .addComponent(jTextFieldCodigo, javax.swing.GroupLayout.PREFERRED_SIZE, 35, javax.swing.GroupLayout.PREFERRED_SIZE))
                            .addGroup(jPanel1Layout.createSequentialGroup()
                                .addComponent(jButtonPrimeiro, javax.swing.GroupLayout.PREFERRED_SIZE, 41, javax.swing.GroupLayout.PREFERRED_SIZE)
                                .addGap(18, 18, 18)
                                .addComponent(jButtonAnterior, javax.swing.GroupLayout.PREFERRED_SIZE, 41, javax.swing.GroupLayout.PREFERRED_SIZE)
                                .addGap(18, 18, 18)
                                .addComponent(jButtonProximo, javax.swing.GroupLayout.PREFERRED_SIZE, 41, javax.swing.GroupLayout.PREFERRED_SIZE)
                                .addGap(18, 18, 18)
                                .addComponent(jButtonUltimo, javax.swing.GroupLayout.PREFERRED_SIZE, 41, javax.swing.GroupLayout.PREFERRED_SIZE)))
                        .addGap(0, 0, Short.MAX_VALUE)))
                .addContainerGap())
        );
        jPanel1Layout.setVerticalGroup(
            jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(jPanel1Layout.createSequentialGroup()
                .addGap(39, 39, 39)
                .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(jLabel2)
                    .addComponent(jTextFieldCodigo, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addGap(18, 18, 18)
                .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(jLabel3)
                    .addComponent(jTextFieldNome, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(jLabel4)
                    .addComponent(jTextFieldSigla, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addGap(28, 28, 28)
                .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING, false)
                    .addComponent(jButtonSair, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                    .addComponent(jButtonNovo, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                    .addComponent(jButtonSalvar, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                    .addComponent(jButtonExcluir, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                    .addComponent(jButtonEditar, javax.swing.GroupLayout.PREFERRED_SIZE, 45, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING)
                    .addComponent(jButtonPrimeiro, javax.swing.GroupLayout.PREFERRED_SIZE, 41, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(jButtonAnterior)
                    .addComponent(jButtonProximo)
                    .addComponent(jButtonUltimo))
                .addGap(18, 18, 18)
                .addComponent(jScrollPane1, javax.swing.GroupLayout.PREFERRED_SIZE, 103, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addContainerGap())
        );

        jButtonEditar.getAccessibleContext().setAccessibleDescription("");

        jLabel1.setFont(new java.awt.Font("Tahoma", 1, 18)); // NOI18N
        jLabel1.setForeground(new java.awt.Color(255, 0, 51));
        jLabel1.setText("Formulário de Cadastro de Estados");

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addContainerGap()
                .addComponent(jPanel1, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                .addContainerGap())
            .addGroup(layout.createSequentialGroup()
                .addGap(90, 90, 90)
                .addComponent(jLabel1)
                .addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
                .addGap(18, 18, 18)
                .addComponent(jLabel1)
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
                .addComponent(jPanel1, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                .addContainerGap())
        );

        setSize(new java.awt.Dimension(512, 452));
        setLocationRelativeTo(null);
    }// </editor-fold>                        
//botão salvar
    private void jButtonSalvarActionPerformed(java.awt.event.ActionEvent evt) {                                              
        try {
            PreparedStatement pst = conexao.conn.prepareCall("insert into estados(nome_estado,sigla_estado)values(?,?)");// passagem do sql para inserção de dados.
            pst.setString(1, jTextFieldNome.getText());// jTextFieldNome é o nome da caixa de texto do formulário, tudo que o usuário digitar nela será salvo. Serve para passagem de parametros.
            pst.setString(2, jTextFieldSigla.getText());
            pst.executeUpdate();//executa a inserção.
            JOptionPane.showMessageDialog(rootPane, "Salvo com sucesso.");
        } catch (SQLException ex) {
            JOptionPane.showMessageDialog(rootPane, "Erro na inserção. \nErro:"+ex.getMessage());
        }
        jTextFieldCodigo.setText("");
        jTextFieldNome.setText("");
        jTextFieldSigla.setText("");
        jTextFieldNome.setEnabled(false);
        jTextFieldSigla.setEnabled(false);
        jButtonEditar.setEnabled(false);
        jButtonExcluir.setEnabled(false);
        jButtonSalvar.setEnabled(false);
        jButtonNovo.setEnabled(true);
    }                                             
//botão excluir
    private void jButtonExcluirActionPerformed(java.awt.event.ActionEvent evt) {                                               
        conexao.executaSQL("delete from estados where sigla_estado= '"+jTextFieldSigla.getText()+"'");//chama metodo da classe conexao banco para realizar a exclusão
        JOptionPane.showMessageDialog(rootPane,"Excluído com sucesso.");
        
        jTextFieldCodigo.setText("");
        jTextFieldNome.setText("");
        jTextFieldSigla.setText("");
        jTextFieldNome.setEnabled(false);
        jTextFieldSigla.setEnabled(false);
        jButtonEditar.setEnabled(false);
        jButtonExcluir.setEnabled(false);
        jButtonSalvar.setEnabled(false);
        jButtonNovo.setEnabled(true);
    }                                              
//botão fechar
    private void jButtonSairActionPerformed(java.awt.event.ActionEvent evt) {                                            
        dispose();//fecha o formulário sem fechar o sistema.
    }                                           
//botão novo
    private void jButtonNovoActionPerformed(java.awt.event.ActionEvent evt) {                                            
        jTextFieldCodigo.setText("");
        jTextFieldNome.setText("");
        jTextFieldSigla.setText("");
        jTextFieldNome.setEnabled(true);
        jTextFieldSigla.setEnabled(true);
        jButtonEditar.setEnabled(true);
        jButtonExcluir.setEnabled(true);
        jButtonSalvar.setEnabled(true);
        jButtonNovo.setEnabled(false);
    }                                           
//botão primeiro   
    private void jButtonPrimeiroActionPerformed(java.awt.event.ActionEvent evt) {                                                
        jButtonEditar.setEnabled(true);
        jButtonExcluir.setEnabled(true);
        try {
            conexao.executaSQL("select * from estados");
            conexao.rs.first();
            jTextFieldCodigo.setText(String.valueOf (conexao.rs.getInt("id_estado")));
            jTextFieldNome.setText(conexao.rs.getString("nome_estado"));
            jTextFieldSigla.setText(conexao.rs.getString("sigla_estado"));
        } catch (SQLException ex) {
            JOptionPane.showMessageDialog(rootPane, "Erro ao mostrar dados. \nErro:"+ex.getMessage());
        }
    }                                               
//botão ultimo
    private void jButtonUltimoActionPerformed(java.awt.event.ActionEvent evt) {                                              
        jButtonEditar.setEnabled(true);
        jButtonExcluir.setEnabled(true);
        try {
            conexao.executaSQL("select * from estados");
            conexao.rs.last();
            jTextFieldCodigo.setText(String.valueOf (conexao.rs.getInt("id_estado")));
            jTextFieldNome.setText(conexao.rs.getString("nome_estado"));
            jTextFieldSigla.setText(conexao.rs.getString("sigla_estado"));
        } catch (SQLException ex) {
            JOptionPane.showMessageDialog(rootPane, "Erro ao mostrar dados. \nErro:"+ex.getMessage());
        }
    }                                             
//botão anterior
    private void jButtonAnteriorActionPerformed(java.awt.event.ActionEvent evt) {                                                
        jButtonEditar.setEnabled(true);
        jButtonExcluir.setEnabled(true);
        try {
            conexao.rs.previous();
            jTextFieldCodigo.setText(String.valueOf (conexao.rs.getInt("id_estado")));
            jTextFieldNome.setText(conexao.rs.getString("nome_estado"));
            jTextFieldSigla.setText(conexao.rs.getString("sigla_estado"));
        } catch (SQLException ex) {
            JOptionPane.showMessageDialog(rootPane, "Erro:"+ex.getMessage());
        }
    }                                               
//botão próximo
    private void jButtonProximoActionPerformed(java.awt.event.ActionEvent evt) {                                               
        jButtonEditar.setEnabled(true);
        jButtonExcluir.setEnabled(true);
        try {
            conexao.rs.next();
            jTextFieldCodigo.setText(String.valueOf (conexao.rs.getInt("id_estado")));
            jTextFieldNome.setText(conexao.rs.getString("nome_estado"));
            jTextFieldSigla.setText(conexao.rs.getString("sigla_estado"));
        } catch (SQLException ex) {
            JOptionPane.showMessageDialog(rootPane, "Erro:"+ex.getMessage());
        }
    }                                              
//botão editar
    private void jButtonEditarActionPerformed(java.awt.event.ActionEvent evt) {                                              
        
    }                                             

    /**
     * @param args the command line arguments
     */
    public static void main(String args[]) {
        /* Set the Nimbus look and feel */
        //<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
        /* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
         * For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html 
         */
        try {
            for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
                if ("Nimbus".equals(info.getName())) {
                    javax.swing.UIManager.setLookAndFeel(info.getClassName());
                    break;
                }
            }
        } catch (ClassNotFoundException ex) {
            java.util.logging.Logger.getLogger(FrmEstado.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (InstantiationException ex) {
            java.util.logging.Logger.getLogger(FrmEstado.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (IllegalAccessException ex) {
            java.util.logging.Logger.getLogger(FrmEstado.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(FrmEstado.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        }
        //</editor-fold>
        //</editor-fold>

        /* Create and display the form */
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new FrmEstado().setVisible(true);
            }
        });
    }

    // Variables declaration - do not modify                     
    private javax.swing.JButton jButtonAnterior;
    private javax.swing.JButton jButtonEditar;
    private javax.swing.JButton jButtonExcluir;
    private javax.swing.JButton jButtonNovo;
    private javax.swing.JButton jButtonPrimeiro;
    private javax.swing.JButton jButtonProximo;
    private javax.swing.JButton jButtonSair;
    private javax.swing.JButton jButtonSalvar;
    private javax.swing.JButton jButtonUltimo;
    private javax.swing.JLabel jLabel1;
    private javax.swing.JLabel jLabel2;
    private javax.swing.JLabel jLabel3;
    private javax.swing.JLabel jLabel4;
    private javax.swing.JPanel jPanel1;
    private javax.swing.JScrollPane jScrollPane1;
    private javax.swing.JTable jTable1;
    private javax.swing.JTextField jTextFieldCodigo;
    private javax.swing.JTextField jTextFieldNome;
    private javax.swing.JTextField jTextFieldSigla;
    // End of variables declaration                   
}

E quando rodo, dá esse problema: run: Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException at Formularios.FrmEstado.jButtonAnteriorActionPerformed(FrmEstado.java:354) at Formularios.FrmEstado.access$700(FrmEstado.java:16) at Formularios.FrmEstado$8.actionPerformed(FrmEstado.java:149) at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2022) at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2346) at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402) at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259) at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252) at java.awt.Component.processMouseEvent(Component.java:6525) at javax.swing.JComponent.processMouseEvent(JComponent.java:3322) at java.awt.Component.processEvent(Component.java:6290) at java.awt.Container.processEvent(Container.java:2234) at java.awt.Component.dispatchEventImpl(Component.java:4881) at java.awt.Container.dispatchEventImpl(Container.java:2292) at java.awt.Component.dispatchEvent(Component.java:4703) at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4898) at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4533) at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4462) at java.awt.Container.dispatchEventImpl(Container.java:2278) at java.awt.Window.dispatchEventImpl(Window.java:2739) at java.awt.Component.dispatchEvent(Component.java:4703) at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:751) at java.awt.EventQueue.access$500(EventQueue.java:97) at java.awt.EventQueue$3.run(EventQueue.java:702) at java.awt.EventQueue$3.run(EventQueue.java:696) at java.security.AccessController.doPrivileged(Native Method) at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:75) at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:86) at java.awt.EventQueue$4.run(EventQueue.java:724) at java.awt.EventQueue$4.run(EventQueue.java:722) at java.security.AccessController.doPrivileged(Native Method) at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:75) at java.awt.EventQueue.dispatchEvent(EventQueue.java:721) at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201) at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116) at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93) at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)

Na verdade o erro é um NullPointerException, olhe

Nessa linha 354 da classe FrmEstado, no método jButtonAnteriorActionPerformed, está vindo tentando acessar algum método de objeto nulo.
Imagino que seja o “rs” do seu “conexao”, verifique.

PS: Nesse tópico de “Certificação Java”, é assunto relacionados a certificação, o local exato para a sua dúvida seia no “Java Básico”