Como Refrescar jTable1 netbeans 6.8

[zetaaster]

Ke tal aqui estoy de nuevo, bueno realice lo que dijiste y al declarar las columnas para modelo en el constructor no me marca error pero cuando ejecuto el programa no me deja hice algo o no se porque cualdo quito esa parte del constuctor si me deja correrlo pero aun asi no se actualiza la tabla.
Pongo el codigo completo solo que lo pongo en dos porque es demasiado y no me deja ponerlo todo.Aqui lo pongo


package pruebas;
import java.sql.*;
import javax.swing.*;
import javax.swing.JTable.*;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;



import javax.swing.table.DefaultTableModel;


public class Alumno1 extends javax.swing.JFrame {


DefaultTableModel modelo;




JTable tabla;
char estado;
Conexion cn;








public Alumno1() {


modelo.addColumn("IdAlumno");
modelo.addColumn("Nombre");
modelo.addColumn("Licenciatura");
modelo.addColumn("Cuatrimestre");

initComponents();
deshabilitar ();

}


public void deshabilitar (){
btnaceptar.setEnabled(false);
btncancelar.setEnabled(false);
txtidalumno.setEnabled(false);
txtnombre.setEnabled(false);
txtcuatrimestre.setEnabled(false);
txtlicenciatura.setEnabled(false);


}

public void habilitar (){
btnaceptar.setEnabled(true);
btncancelar.setEnabled(true);

txtidalumno.setEnabled(true);
txtnombre.setEnabled(true);
txtcuatrimestre.setEnabled(true);
txtlicenciatura.setEnabled(true);

}

public void desBotones(){
btnnuevo.setEnabled(false);
btnmodificar.setEnabled(false);
btneliminar.setEnabled(false);
}


public void habBotones(){
btnnuevo.setEnabled(true);
btnmodificar.setEnabled(true);
btneliminar.setEnabled(true);
}


/** 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() {
bindingGroup = new org.jdesktop.beansbinding.BindingGroup();

escuelaPUEntityManager = java.beans.Beans.isDesignTime() ? null : javax.persistence.Persistence.createEntityManagerF actory("escuelaPU").createEntityManager();
alumnoQuery = java.beans.Beans.isDesignTime() ? null : escuelaPUEntityManager.createQuery("SELECT a FROM Alumno a");
alumnoList = java.beans.Beans.isDesignTime() ? java.util.Collections.emptyList() : alumnoQuery.getResultList();
jPanel1 = new javax.swing.JPanel();
jScrollPane1 = new javax.swing.JScrollPane();
jTable1 = new javax.swing.JTable();
jLabel1 = new javax.swing.JLabel();
txtidalumno = new javax.swing.JTextField();
txtnombre = new javax.swing.JTextField();
jLabel2 = new javax.swing.JLabel();
txtlicenciatura = new javax.swing.JTextField();
jLabel3 = new javax.swing.JLabel();
txtcuatrimestre = new javax.swing.JTextField();
jLabel4 = new javax.swing.JLabel();
btnnuevo = new javax.swing.JButton();
btncancelar = new javax.swing.JButton();
btneliminar = new javax.swing.JButton();
btnmodificar = new javax.swing.JButton();
btnaceptar = new javax.swing.JButton();

setDefaultCloseOperation(javax.swing.WindowConstan ts.EXIT_ON_CLOSE);
setName("Form"); // NOI18N

jPanel1.setName("jPanel1"); // NOI18N

jScrollPane1.setName("jScrollPane1"); // NOI18N

jTable1.setName("jTable1"); // NOI18N

org.jdesktop.swingbinding.JTableBinding jTableBinding = org.jdesktop.swingbinding.SwingBindings.createJTab leBinding(org.jdesktop.beansbinding.AutoBinding.Up dateStrategy.READ_WRITE, alumnoList, jTable1);
org.jdesktop.swingbinding.JTableBinding.ColumnBind ing columnBinding = jTableBinding.addColumnBinding(org.jdesktop.beansb inding.ELProperty.create("${idAlumno}"));
columnBinding.setColumnName("Id Alumno");
columnBinding.setColumnClass(String.class);
columnBinding = jTableBinding.addColumnBinding(org.jdesktop.beansb inding.ELProperty.create("${nombre}"));
columnBinding.setColumnName("Nombre");
columnBinding.setColumnClass(String.class);
columnBinding = jTableBinding.addColumnBinding(org.jdesktop.beansb inding.ELProperty.create("${licenciatura}"));
columnBinding.setColumnName("Licenciatura");
columnBinding.setColumnClass(String.class);
columnBinding = jTableBinding.addColumnBinding(org.jdesktop.beansb inding.ELProperty.create("${cuatrimestre}"));
columnBinding.setColumnName("Cuatrimestre");
columnBinding.setColumnClass(String.class);
bindingGroup.addBinding(jTableBinding);
jTableBinding.bind();
jTable1.addMouseListener(new java.awt.event.MouseAdapter() {
public void mouseClicked(java.awt.event.MouseEvent evt) {
jTable1MouseClicked(evt);
}
});
jScrollPane1.setViewportView(jTable1);

org.jdesktop.application.ResourceMap resourceMap = org.jdesktop.application.Application.getInstance(p ruebas.PruebasApp.class).getContext().getResourceM ap(Alumno1.class);
jLabel1.setText(resourceMap.getString("jLabel1.tex t")); // NOI18N
jLabel1.setName("jLabel1"); // NOI18N

txtidalumno.setText(resourceMap.getString("txtidal umno.text")); // NOI18N
txtidalumno.setName("txtidalumno"); // NOI18N
txtidalumno.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
txtidalumnoActionPerformed(evt);
}
});