Add Object to Jcombobox

Question

I’m trying to add an object in the jCombo box, but, it’s saying showing the message that the Object cannot be converted to String, being that I’m using the public String toString()

Follow the Model code:

public class Model(){
  private int codigo;
  private String nome;
  public int getCodigo(){ return this.codigo; }
  public void setCodigo(int codigo){ this.codigo = codigo; }
  public String getNome(){ return this.nome; }
  public void setNome(String nome){ this.nome = nome; }
  @Override
  public String toString(){ return nome; }
}

Dao:

public class Model_DAO {
     public List<Model> getListModel(){
            List lista = new ArrayList();
            connection = ConnectionFactory.getConnection();
            sql = "SELECT id, nome FROM model ";
            try {
                stmt = connection.prepareStatement(sql);
                rs = stmt.executeQuery();
                while( rs.next() ){
                   Model model = new Model();
                   model.setId( rs.getInt( "id" ) );
                   model.setNome( rs.getString("nome") );
                   lista.add( model );
                }
                connection.close();
            } catch (SQLException ex) {
                Logger.getLogger(EnergiaDAO.class.getName()).log(Level.SEVERE, null, ex);
            }
            return lista;
        }
}

Completion of the Combobox

public class TelaClasse {
    public TelaClasse(){
      popularComboMedidor();
      JFrame tela = new JFrame();
      tela.add( jc_model );
    }
    JCombobox jC_model = new JComboBox(); 

    private void popularComboMedidor(){

            Model_DAO md = new Model_DAO();
            List lista = md.getListModel();
            Iterator it = lista.iterator();
            jC_model.removeAllItems(); //JC jCombobox        
            while( it.hasNext() ){
              Model model = (Model) it.next();
              //  System.out.println(model);
              jC_model.addItem( model );
            }
        }
   } 

Remembering that I have always done so, in this other computer that I am using is not working. The method toString() is only working with System.out.println()