Bloquear coluna para digitação de texto

alguém sabe me dizer pq não consigo colocar coluna acima de 3? sempre q coloco da o seguinte erro
"Exception in thread “AWT-EventQueue-0” java.lang.ArrayIndexOutOfBoundsException: 30 >= 4"

TableColumn col = tabela.getColumnModel().getColumn(1);
col.setCellEditor(new MyTableCellEditor());
class MyTableCellEditor extends AbstractCellEditor
  implements TableCellEditor{
  JComponent component = new JTextField();
  public boolean stopCellEditing(){
    String s = (String)getCellEditorValue();
    boolean valido = true;
    for(int i = 0; i < s.length(); i++){
      Character caractere = s.charAt(i);
      if(!Character.isDigit(caractere)){
        valido = false;
        break;
      }
    }    
    if(!valido){
      JOptionPane.showMessageDialog(null, 
         "Valor inválido");
      return false; 
    }
    return super.stopCellEditing();
  }
  public Component getTableCellEditorComponent(
    JTable table, Object value,
    boolean isSelected, int rowIndex, int vColIndex){
    if(isSelected){
      //
    }
    ((JTextField)component).setText((String)value);
    return component;
  }
  public Object getCellEditorValue() {
    return ((JTextField)component).getText();
  }
}