Help with JComboBox-JTable

Question

Hi there!
I'll try to explain my problem the best I can, I hope you can understand me so you may get to help me, I'd really appreciate it. I'm trying to make a JTable to render a cell as a JComboBox, that's ok and it's working fine. The problem comes when I try to change the combo value. The itemStateChanged method is supposed to get some values from a database, if the first is bigger than the second it shows an alert, else it makes an update to the database. Now, the problem is that, if the combobox default value is blank (""), it works fine, but if it's filled with something as a name ("anything") it automatically shows the alert, even if I'm not changing the combo value. The second problem is that it shows the alert twice, I'll try to explain with code:
class Cambia_Cita extends javax.swing.AbstractCellEditor implements javax.swing.table.TableCellEditor ,java.awt.event.ItemListener{
    protected EventListenerList listenerList = new EventListenerList();
    protected ChangeEvent changeEvent = new ChangeEvent(this);   
    protected javax.swing.JComboBox combo = new javax.swing.JComboBox();
    int i;
    String valor = "";
    int j;
    javax.swing.JTable tabla = new javax.swing.JTable();
    public Cambia_Cita() {
        super();
        combo.addItemListener(this);
        Base base = new Base();
        Statement sta = base.conectar();
        try {
            ResultSet rs = sta.executeQuery("SELECT DISTINCT Nombre_Completo FROM Pacientes WHERE Alta = 'n'");
            combo.addItem("");
            while(rs.next())
                combo.addItem(rs.getString("Nombre_Completo"));
        }catch(SQLException e) {
            System.out.println (e.getMessage());
        } finally {
            base.cerrar(sta);
        combo.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent event) {
                System.out.println("algo");
                tabla.setValueAt(valor,i,j);
    public Object getCellEditorValue() {
        return(combo.getSelectedItem());
    public java.awt.Component getTableCellEditorComponent(javax.swing.JTable table, Object value, boolean isSelected, int row, int column) {
        i = row;
        j = column;
        tabla = table;
        valor = value.toString();
        combo.setSelectedItem(tabla.getValueAt(i,j));
        System.out.println (i + "," + j);
        java.awt.Component c = table.getDefaultRenderer(String.class).getTableCellRendererComponent(table, value, isSelected, false, row, column);
        if (c != null) {
            combo.setBackground(c.getBackground());
        return combo;
    public void itemStateChanged(java.awt.event.ItemEvent e) {
        Base base = new Base();
        Statement sta = base.conectar();
        try {
            String asist;
            if (tabla.getValueAt(i,3).equals(new Boolean(true))) {
                asist = "s";
            } else {
                asist = "n";
            ResultSet rs = sta.executeQuery("SELECT COUNT(ID_Cita) FROM Cita JOIN Pacientes ON Cita.RFC_Paciente " +
                    "= Pacientes.RFC_Paciente WHERE Nombre_Completo = '" + combo.getSelectedItem() + "'");
            rs.next();
            int result = rs.getInt("COUNT(ID_Cita)");
            rs = sta.executeQuery("SELECT Consultas FROM Ciclo JOIN Pacientes ON Ciclo.RFC_Paciente = Pacientes." +
                    "RFC_Paciente WHERE Nombre_Completo = '"+ combo.getSelectedItem() +"' AND Ciclo.Numero_Ciclo = " +
                    "Pacientes.Ciclo");
            rs.next();
            int maximo = rs.getInt("Consultas");
            /* if maximo is bigger than result plus 1, then it shows the alert, but it is shown even if I don't change the combo value!!!, this part only works if the default value of the combo is blank */
            if (maximo >= result +1 ) {
                sta.executeUpdate("UPDATE Cita,Pacientes SET Cita.RFC_Paciente = Pacientes.RFC_Paciente WHERE " +
                        "Nombre_Completo = '" + combo.getSelectedItem() + "' AND ID_Cita = " + tabla.getValueAt(i,0));
            }else
                javax.swing.JOptionPane.showMessageDialog(null,"No se puede agregar otra cita...");
        }catch (ArrayIndexOutOfBoundsException ex) {
            System.out.println (ex.getMessage());
        } catch (SQLException ex) {
            System.out.println (ex.getMessage());
        } finally {
            base.cerrar(sta);
}So, I'd like to know why the alert appears twice when it works and why it appears even if the combo value ain't changed. I really hope anyone can help me. Thank you!

Answer 1

if the first is bigger than the second it shows an alertIf you want to know when data is changed in the table then you use a TableModelListener, not an ItemListener. Here is a simple example:
http://forum.java.sun.com/thread.jspa?forumID=57&threadID=566133
If you need further help then you need to create a [url http://homepage1.nifty.com/algafield/sscce.html]Short, Self Contained, Compilable and Executable, Example Program (SSCCE) that demonstrates the incorrect behaviour, because I can't guess exactly what you are doing based on the information provided.
And don't forget to use the [url http://forum.java.sun.com/help.jspa?sec=formatting]Code Formatting Tags so the code retains its original formatting.