Adicionar os dados na tabela

package controle;

import java.awt.event.<em>;

import javax.swing.</em>;

import javax.swing.table.*;

import java.awt.event.ActionListener;

import java.util.ArrayList;

import java.util.Vector;

import java.sql.SQLException;

import java.sql.ResultSet;

private JFrame tela;
private Aluno a;	
private DaoAluno daoAluno;
private JPanel painel;
private ArrayList<Aluno> listaAluno;




public ControleTelaAluno(JFrame tela) {
	this.tela=tela;
}


public void actionPerformed(ActionEvent e) {
	JPanel painel = (JPanel)tela.getContentPane().getComponent(0);
	JTextField mat  = (JTextField)painel.getComponent(1) ;
	JTextField nome  = (JTextField)painel.getComponent(3);
	JTextField tel  = (JTextField)painel.getComponent(5);
	JTextField dataNasc  = (JTextField)painel.getComponent(7);
	
	JScrollPane spainel = (JScrollPane)painel.getComponent(8);
	JViewport jv = (JViewport)spainel.getComponent(0);
	JTable tabela = (JTable)jv.getComponent(0);
	
	DefaultTableModel dtm = (DefaultTableModel)tabela.getModel();
	
	Aluno a = new Aluno();

	
	a.setMat(mat.getText());
	a.setNome(nome.getText());
	a.setTel(tel.getText());
	a.setDataNasc(dataNasc.getText());
	
	DaoAluno dao = new DaoAluno();
	
	if (e.getActionCommand().equals("cadastrar")){
		
		dao.cadastrar(a);
		dtm.addRow( new String[]{a.getMat(),a.getNome(),a.getTel(),a.getDataNasc()});
		
		   }

		 
	
	if(e.getActionCommand().equals("Excluir")){				
		dao.excluir(a);
		for(int i=0;i<dtm.getRowCount();i++){
			if(a.getMat().equals(dtm.getValueAt(i,0))){
				dtm.removeRow(i);
				break;
			}
		}

	}
	
		
	
		
	if(e.getActionCommand().equals("Consultar")){		
		a = dao.consultar(a);
		if(a==null){
			JOptionPane.showMessageDialog(null,"Não encontrado!");
		}else{
			mat.setText(a.getMat());
			nome.setText(a.getNome());
			tel.setText(a.getTel());
			dataNasc.setText(a.getDataNasc());				
		}		
}

for(int i=0 ; i<dtm.getRowCount() ; i++){
	if(dtm.getValueAt(i,0).equals(a.getMat())){					
		dtm.setValueAt(a.getNome(),i,1);
		dtm.setValueAt(a.getTel(),i,2);
		dtm.setValueAt(a.getDataNasc(),i,3);
		break;