Item listener & combo boxes......please help me....thanks

Question

I did a applet that shows 4 jcombobox......the combo 2 is filling if the combo 1 is actioned, the combo3 is filling if the combo2 is actioned and the combo 4 have to be filled if the combo 3 is actioned.
I did it...using item listener......it works fine....the first time....(in the console appears the lines that i specify using System.out.println).....but after...when i select any combo....i see in the console...that the itemlistener action is done several times......i don�t know why......do you have any idea or suggestion about it?............
Thanks in advance...
Mary
This is the code:
import java.io.*;
import java.net.*;
import java.util.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.tree.*;
import javax.swing.border.*;
import javax.swing.event.*;
import java.lang.*;
import java.text.NumberFormat;
import java.text.DecimalFormat;
public class w3_a extends JApplet {
Container contentPane;
int i=10, j=20, k=30, l=40;
private JComboBox jcb1;
private JComboBox jcb2;
private JComboBox jcb3;
private JComboBox jcb4;
private JTabbedPane jtp;
private GriddedPanel jp1;
private GriddedPanel jp2;
public void init() {
contentPane = getContentPane();
contentPane.setLayout(new BorderLayout());
add_JComboBoxes_GUI();
add_JTabbedPanes_GUI();
fill_combo1();
void add_JComboBoxes_GUI() {
jp1 = new GriddedPanel();
jp1.setBorder( new EmptyBorder(new Insets(5, 5, 5, 5)) );
jcb1 = new JComboBox();
jcb2 = new JComboBox();
jp1.add(jcb1);
jp1.add(jcb2);
contentPane.add(jp1, BorderLayout.NORTH);
jcb1.addItemListener(new java.awt.event.ItemListener() {
public void itemStateChanged(ItemEvent e) {
System.out.println("Accion 1 - Element");
fill_combo2();
jcb2.addItemListener(new java.awt.event.ItemListener() {
public void itemStateChanged(ItemEvent e) {
System.out.println("Accion 2 - Element");
fill_combo3();
void add_JTabbedPanes_GUI() {
jtp = new JTabbedPane();
jtp.addTab("Datos Generales", new Panel_Data());
contentPane.add(jtp);
class Panel_Data extends JPanel {
public Panel_Data() {
// Primer panel de JTabbedPane de Datos Generales
jp2 = new GriddedPanel();
jp2.setBorder( new EmptyBorder(new Insets(5, 5, 5, 5)) );
jcb3 = new JComboBox();
jcb4 = new JComboBox();
jp2.add(jcb3);
jp2.add(jcb4);
jtp.add(jp2);
contentPane.add(jtp, BorderLayout.SOUTH);
jcb3.addItemListener(new java.awt.event.ItemListener() {
public void itemStateChanged(ItemEvent e) {
System.out.println("Accion 3 - Element");
fill_combo4();
jcb4.addItemListener(new java.awt.event.ItemListener() {
public void itemStateChanged(ItemEvent e) {
System.out.println("Accion 4 - Element");
void fill_combo1() {
System.out.println("Start fill_combo1()");
jcb1.removeAllItems();
jcb1.addItem("combo1 " + (++i));
jcb1.addItem("combo1 " + (++i));
jcb1.addItem("combo1 " + (++i));
System.out.println("End fill_combo1()");
return;
void fill_combo2() {
System.out.println("Start fill_combo2()");
jcb2.removeAllItems();
jcb2.addItem("combo2 " + (++j));
jcb2.addItem("combo2 " + (++j));
jcb2.addItem("combo2 " + (++j));
System.out.println("End fill_combo2()");
return;
void fill_combo3() {
System.out.println("Start fill_combo3()");
jcb3.removeAllItems();
jcb3.addItem("combo3 " + (++k));
jcb3.addItem("combo3 " + (++k));
jcb3.addItem("combo3 " + (++k));
System.out.println("End fill_combo3()");
return;
void fill_combo4() {
System.out.println("Start fill_combo4()");
jcb4.removeAllItems();
jcb4.addItem("combo4 " + (++l));
jcb4.addItem("combo4 " + (++l));
jcb4.addItem("combo4 " + (++l));
System.out.println("End fill_combo4()");
return;

Answer 1

Hi!!!
Thanks by answer to me.....
Yes ...i already understand why is happening in it.....
I did modifications to my code to remove the listeners and after to add them....but no yet obtain my goal that the combo 2 is filling if the combo 1 is actioned, the combo3 is filling if the combo2 is actioned and the combo 4 have to be filled if the combo 3 is actioned.
I think that at least should it to work for combo1 and combo2, because i don't know how to specify to add or remove the listener from the class de Panel_Data would be .....because i think that with:
jcb3.removeItemListener(this);
jcb3.addItemListener(this);
jcb4.removeItemListener(this);
jcb4.addItemListener(this);
i am removing and adding the itemlistener from the main class w10_a (for combo3 and combo4)...... and not for the Panel_Data class.
ie,
jcb4.removeItemListener(
//here is my doubt i don't know how to specify
//to add or to remove the itemlistener from the
//Panel_Data class for combo3 and combo4
jcb4.addItemListener(
//here is my doubt i don't know how to specify
//to add or to remove the itemlistener from the
//Panel_Data class for combo3 and combo4
Well...i hope that you could help me please in give me some suggestions about it...
Thanks in advance...
Mary
Here is my code modified:
import java.io.*;
import java.net.*;
import java.util.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.tree.*;
import javax.swing.border.*;
import javax.swing.event.*;
import java.lang.*;
import java.text.NumberFormat;
import java.text.DecimalFormat;
public class w10_a extends JApplet implements ItemListener{
Container contentPane;
int i=10, j=20, k=30, l=40;
private JComboBox jcb1;
private JComboBox jcb2;
private JComboBox jcb3;
private JComboBox jcb4;
private JTabbedPane jtp;
private GriddedPanel jp1;
private GriddedPanel jp2;
public void init() {
contentPane = getContentPane();
contentPane.setLayout(new BorderLayout());
add_JComboBoxes_GUI();
add_JTabbedPanes_GUI();
fill_combo1();
void add_JComboBoxes_GUI() {
jp1 = new GriddedPanel();
jp1.setBorder( new EmptyBorder(new Insets(5, 5, 5, 5)) );
jcb1 = new JComboBox();
jcb2 = new JComboBox();
jp1.add(jcb1);
jp1.add(jcb2);
contentPane.add(jp1, BorderLayout.NORTH);
jcb1.addItemListener(this);
jcb2.addItemListener(this);
void add_JTabbedPanes_GUI() {
jtp = new JTabbedPane();
jtp.addTab("Datos Generales", new Panel_Data());
contentPane.add(jtp);
class Panel_Data extends JPanel implements ItemListener {
public Panel_Data() {
// Primer panel de JTabbedPane de Datos Generales
jp2 = new GriddedPanel();
jp2.setBorder( new EmptyBorder(new Insets(5, 5, 5, 5)) );
jcb3 = new JComboBox();
jcb4 = new JComboBox();
jp2.add(jcb3);
jp2.add(jcb4);
jtp.add(jp2);
contentPane.add(jtp, BorderLayout.SOUTH);
//Implementamos ActionListener para cada acci�n ejecutada
jcb3.addItemListener(this);
jcb4.addItemListener(this);
public void itemStateChanged(ItemEvent e) {
if ( e.getItemSelectable() == jcb3 ) {
System.out.println("Accion 3 - Element");
fill_combo4();
if ( e.getItemSelectable() == jcb4 ) {
System.out.println("Accion 4 - Element");
public void itemStateChanged(ItemEvent e) {
if ( e.getItemSelectable() == jcb1 ) {
System.out.println("Accion 1 - Element");
fill_combo2();
if ( e.getItemSelectable() == jcb2 ) {
System.out.println("Accion 2 - Element");
fill_combo3();
void fill_combo1() {
System.out.println("Start fill_combo1()");
jcb1.removeItemListener(this);
jcb1.removeAllItems();
jcb1.addItem("combo1 " + (++i));
jcb1.addItem("combo1 " + (++i));
jcb1.addItemListener(this);
jcb1.addItem("combo1 " + (++i));
System.out.println("End fill_combo1()");
void fill_combo2() {
System.out.println("Start fill_combo2()");
jcb2.removeItemListener(this);
jcb2.removeAllItems();
jcb2.addItem("combo2 " + (++j));
jcb2.addItem("combo2 " + (++j));
jcb2.addItemListener(this);
jcb2.addItem("combo2 " + (++j));
System.out.println("End fill_combo2()");
void fill_combo3() {
System.out.println("Start fill_combo3()");
jcb3.removeItemListener(this);
jcb3.removeAllItems();
jcb3.addItem("combo3 " + (++k));
jcb3.addItem("combo3 " + (++k));
jcb3.addItemListener(this);
jcb3.addItem("combo3 " + (++k));
System.out.println("End fill_combo3()");
void fill_combo4() {
System.out.println("Start fill_combo4()");
jcb4.removeItemListener(this);
jcb4.removeAllItems();
jcb4.addItem("combo4 " + (++l));
jcb4.addItem("combo4 " + (++l));
jcb4.addItemListener(this);
jcb4.addItem("combo4 " + (++l));
System.out.println("End fill_combo4()");