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How to add price on an item from a binded ComboBox?

I'm trying to learn the difference between Hashtable and HashMap and I'm trying to add specific prices to these items here. The goal is to print the price of the item selected from comboItem into txtPrice.
String[] items = {"Select Item","Betta Fish","Snail","Supplies","Food"};
comboGroup = new JComboBox<String>(items);
comboGroup.addActionListener(this);
comboGroup.setBounds(130,35,150,40);
comboItem = new JComboBox<>();
comboItem.setPrototypeDisplayValue("XXXXXXXXXXX");
comboItem.setBounds(130,85,150,40);
String[] subItems1 = {"Select Betta","Plakat","Halfmoon","Double Tail","Crown Tail"};
subItems.put(items[1], subItems1);
String[] subItems2 = {"Select Snail","Pond Snail","Ramshorn","Apple Snail","Assassin Snail"};
subItems.put(items[2], subItems2);
String[] subItems3 = {"Select Supply","Small Fine Net","Large Fine Net","Flaring Mirror","Aquarium Hose (1meter)"};
subItems.put(items[3], subItems3);
String[] subItems4 = {"Select Food","Daphnia","Tubifex","Mosquito Larvae","Optimum Pellets"};
subItems.put(items[4], subItems4);
comboGroup.setSelectedIndex(1);
//TextFields <- this is the attempt to add price to subItems value but commented out
/*int[] items1price = {0,150,350,200,200};
subItems.put(items[1], items1price);
int[] items2price = {0,15,25,80,120};
subItems.put(items[2], items2price);
int[] items3price = {0,50,80,25,15};
subItems.put(items[3], items3price);
int[] items4price = {0,50,100,50,50};
subItems.put(items[4], items4price);
comboGroup.setSelectedIndex(1);
*/
txtPrice = new JTextField();
txtPrice.setBounds(130,135,150,40);
So far with my understanding from HashMap applying it to CLi and not in GUI, If I try HashMap<String,Integer> I can only print it altogether in a single line.
eg.
HashMap<String,Integer> item = new HashMap<String,Integer>();
item.put("Plakat",50);
CLi Prints:
Plakat=50
What I want is to print Plakat from selected comboItem then print 50 to txtPrice but I don't know how to do that.
The whole code is here: https://github.com/kontext66/GuwiPos
GUI and Main.
Additional note: I am a beginner and I'm trying to understand Layout Manager for now, so the code here is a bit messy and literal.

Below is an example using JComboBox and HashMap to get the corresponding "prices" to specific items in the combo box. I would suggest going through the tutorial on How to Use Various Layout Managers and choose the ones that suit you best. As for the difference between HashMap and HashTable, please have a look at this answer. The main difference is that HashTable is synchronized, whereas HashMap is not, and since synchronization is not an issue for you, I'd suggest HashMap. Also, another option would be to add instances of a custom object to a JComboBox, as described here. Thus, there would be no need to use HashMap.
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
import java.util.*;
public class App {
Map<String, String> map;
JTextField tf;
public App() {
map = new HashMap<String, String>();
map.put("Plakat", "50");
map.put("Halfmoon", "25");
map.put("Double Tail", "80");
}
private void addComponentsToPane(Container pane) {
String[] items = { "Select Item", "Plakat", "Halfmoon", "Double Tail" };
JComboBox<String> comboBox = new JComboBox<String>(items);
comboBox.addItemListener(new ItemListener() {
public void itemStateChanged(ItemEvent event) {
if (event.getStateChange() == ItemEvent.SELECTED) {
String item = (String) event.getItem();
System.out.println(item);
tf.setText(map.get(item));
}
}
});
tf = new JTextField();
JPanel p = new JPanel();
pane.add(comboBox, BorderLayout.NORTH);
pane.add(tf, BorderLayout.SOUTH);
}
private void createAndShowGUI() {
JFrame frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
addComponentsToPane(frame.getContentPane());
// frame.setSize(640, 480);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
public static void main(String[] args) {
javax.swing.SwingUtilities.invokeLater(new Runnable() {
public void run() {
new App().createAndShowGUI();
}
});
}
}
Update
Below is the implementation of the second approach described earlier, where a custom object is used for adding items to a JComboBox, and hence, there is no need to use a HashMap.
P.S. I should also add that if the user shouldn't be allowed to edit the "price" in the text field, then you should use tf.setEditable(false);, or even use a JLabel instead.
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
public class App {
JTextField tf;
class ComboItem {
private String key;
private String value;
public ComboItem(String key, String value) {
this.key = key;
this.value = value;
}
#Override
public String toString() {
return key;
}
public String getKey() {
return key;
}
public String getValue() {
return value;
}
}
private void addComponentsToPane(Container pane) {
JComboBox<ComboItem> comboBox = new JComboBox<ComboItem>();
comboBox.addItem(new ComboItem("Select Item", ""));
comboBox.addItem(new ComboItem("Plakat", "50"));
comboBox.addItem(new ComboItem("Halfmoon", "25"));
comboBox.addItem(new ComboItem("Double Tail", "80"));
comboBox.addItemListener(new ItemListener() {
public void itemStateChanged(ItemEvent event) {
if (event.getStateChange() == ItemEvent.SELECTED) {
Object item = comboBox.getSelectedItem();
String value = ((ComboItem) item).getValue();
tf.setText(value);
}
}
});
tf = new JTextField();
JPanel p = new JPanel();
pane.add(comboBox, BorderLayout.NORTH);
pane.add(tf, BorderLayout.SOUTH);
}
private void createAndShowGUI() {
JFrame frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
addComponentsToPane(frame.getContentPane());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
public static void main(String[] args) {
javax.swing.SwingUtilities.invokeLater(new Runnable() {
public void run() {
new App().createAndShowGUI();
}
});
}
}
Update 2
To convert the string from the text field into double, you can use Double.parseDouble(String), as shown below (again, make sure to use tf.setEditable(false);, so that the value cannot be modified by the user).
double price = 0;
if (tf.getText() != null && !tf.getText().trim().isEmpty())
price = Double.parseDouble(tf.getText());
System.out.println(price);

Trouble with listener in Java. I have a drop down box not passing the users selection like I need

I have a project for class due this Wednesday and am having trouble with a few things: I have two if else statements that control the values presented in two different drop down menus. To me, it appears I'm not getting the information of of the previous drop down(there are two drop downs in which affects the values presented in the next).
Here's my code thus far:
///Occupancy///
JLabel label2 = new JLabel("Please Select the Number of Occupants");
JComboBox occupancy_list = new JComboBox(occupancy_string);
occupancy_list.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent event)//Listener for Occupancy Drop Down
{
JComboBox cb = (JComboBox)event.getSource(); //grab the user selection
String selection = (String) cb.getSelectedItem();
int number = Integer.parseInt((String) selection);
}
});
String selection = (String) occupancy_list.getSelectedItem();
int number = Integer.parseInt((String) selection);
if(number>2)
{
style=(style2);
}
else
{
style=(style1);
}
///Room Type///
JLabel label3 = new JLabel("Please Select a Room Style");
//Creates RoomStyle Drop Down
JComboBox room_type = new JComboBox(style);
roomtype_string=(String) room_type.getSelectedItem();
room_type.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent event)//Listener for Room Style Drop Down
{
JComboBox cb = (JComboBox)event.getSource(); //grab the user selection
String selection = (String) cb.getSelectedItem();
}
});
String selection2 = (String) room_type.getSelectedItem();
if(selection2.equals("Cabin"))
{
room_number=(cabin_string);
}
else
{
room_number=(suite_string);
}
///Room Selection///
JLabel label4 = new JLabel("Please Select a Room");
//Creates RoomNumber Drop Down
JComboBox room_list = new JComboBox(room_number);
roomselected = (String) room_list.getSelectedItem();
room_list.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent event)//Listener for Occupancy Drop Down
{
JComboBox cb = (JComboBox)event.getSource(); //grab the user selection
String selection = (String) cb.getSelectedItem();
}
});
String selection3 = (String) room_list.getSelectedItem();
//Dining
JLabel label5 = new JLabel("Please Select a Dining Time");
JComboBox dining_list = new JComboBox(dining_string);
dining_list.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent event)//Listener for Occupancy Drop Down
{
JComboBox cb = (JComboBox)event.getSource(); //grab the user selection
String selection = (String) cb.getSelectedItem();
}
});
String selection4 = (String) dining_list.getSelectedItem();
NOTE: I have since rewritten my code, still no dice:
` //Creates subPanel2 with Occupancy, Room Type, Room, and Dining Time request
JPanel subpanel = new JPanel();
///Occupancy///
JLabel label2 = new JLabel("Please Select the Number of Occupants");
JComboBox occupancy_list = new JComboBox(occupancy_string);
Occupancy_Listener occupancy = new Occupancy_Listener();
occupancy_list.addActionListener(occupancy);
//updateStyle(occupancy_string[occupancy_list.getSelectedIndex()]);
///Room Type///
JLabel label3 = new JLabel("Please Select a Room Style");
//Creates RoomStyle Drop Down
JComboBox room_type = new JComboBox(style);
Style_Listener styleListen = new Style_Listener();
room_type.addActionListener(styleListen);
//updateNumber(style[room_type.getSelectedIndex()]);
///Room Selection///
JLabel label4 = new JLabel("Please Select a Room");
//Creates RoomNumber Drop Down
JComboBox room_list = new JComboBox(room_number);
Room_Listener room = new Room_Listener();
room_list.addActionListener(room);
//updateRoom(room_number[room_list.getSelectedIndex()]);
//Dining
JLabel label5 = new JLabel("Please Select a Dining Time");
JComboBox dining_list = new JComboBox(dining_string);
Din_Listener dining = new Din_Listener();
dining_list.addActionListener(dining);
//updateDin(dining_string[dining_list.getSelectedIndex()]);
...
...
...
...
...
}
private class Occupancy_Listener implements ActionListener
{
public void actionPerformed(ActionEvent event)//Listener for Occupancy Drop Down
{
JComboBox cb = (JComboBox)event.getSource(); //grab the user selection
String selection = (String) cb.getSelectedItem();
System.out.println(selection);
System.out.println(style[0]);
System.out.println(room_number[0]);
updateStyle(selection);
}
}
private class Style_Listener implements ActionListener
{
public void actionPerformed(ActionEvent event)//Listener for Occupancy Drop Down
{
JComboBox cb = (JComboBox)event.getSource(); //grab the user selection
String selection = (String) cb.getSelectedItem();
updateNumber(selection);
}
}
private class Room_Listener implements ActionListener
{
public void actionPerformed(ActionEvent event)//Listener for Occupancy Drop Down
{
JComboBox cb = (JComboBox)event.getSource(); //grab the user selection
String selection = (String) cb.getSelectedItem();
updateRoom(selection);
}
}
private class Din_Listener implements ActionListener
{
public void actionPerformed(ActionEvent event)//Listener for Occupancy Drop Down
{
JComboBox cb = (JComboBox)event.getSource(); //grab the user selection
String selection = (String) cb.getSelectedItem();
updateDin(selection);
}
}
protected void updateStyle(String pick)
{
String[] style1 ={"Cabin", "Suite"};
String[] style2 ={"Suite"};
//ocu_string=pick;
number = Integer.parseInt(pick);
if(number>2)
{
style=style2;
}
else
{
style=style1;
}
}
protected void updateNumber(String pick)
{
String[] cabin_string = {"11-1","11-2","11-3","11-4","11-5","11-6","11-7","11-8","11-9","11-10"};
String[] suite_string = {"11-S1","11-S2"};
type=pick;
if(type.equals("cabin"))
{
room_number=cabin_string;
}
else
{
room_number=suite_string;
}
}
protected void updateRoom(String pick)
{
room_num=pick;
}
protected void updateDin(String pick)
{
din_time=pick;
}
//public String getPopulation()
{
//return ocu_string;
}

This might be what your are asking. You select an item from the first combo box and it populates items in a second combo box:
import java.awt.*;
import java.awt.event.*;
import java.util.*;
import javax.swing.*;
public class ComboBoxTwo extends JPanel implements ActionListener
{
private JComboBox<String> mainComboBox;
private JComboBox<String> subComboBox;
private Hashtable<String, String[]> subItems = new Hashtable<String, String[]>();
public ComboBoxTwo()
{
String[] items = { "Select Item", "Color", "Shape", "Fruit" };
mainComboBox = new JComboBox<String>( items );
mainComboBox.addActionListener( this );
// prevent action events from being fired when the up/down arrow keys are used
mainComboBox.putClientProperty("JComboBox.isTableCellEditor", Boolean.TRUE);
add( mainComboBox );
// Create sub combo box with multiple models
subComboBox = new JComboBox<String>();
subComboBox.setPrototypeDisplayValue("XXXXXXXXXX"); // JDK1.4
add( subComboBox );
String[] subItems1 = { "Select Color", "Red", "Blue", "Green" };
subItems.put(items[1], subItems1);
String[] subItems2 = { "Select Shape", "Circle", "Square", "Triangle" };
subItems.put(items[2], subItems2);
String[] subItems3 = { "Select Fruit", "Apple", "Orange", "Banana" };
subItems.put(items[3], subItems3);
}
public void actionPerformed(ActionEvent e)
{
String item = (String)mainComboBox.getSelectedItem();
Object o = subItems.get( item );
if (o == null)
{
subComboBox.setModel( new DefaultComboBoxModel() );
}
else
{
subComboBox.setModel( new DefaultComboBoxModel( (String[])o ) );
}
}
private static void createAndShowUI()
{
JFrame frame = new JFrame("SSCCE");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add( new ComboBoxTwo() );
frame.setLocationByPlatform( true );
frame.pack();
frame.setVisible( true );
}
public static void main(String[] args)
{
EventQueue.invokeLater(new Runnable()
{
public void run()
{
createAndShowUI();
}
});
}
}

You may be confused by the fact that code inside anonymous classes (or local classes) is not executed at the same time as the code around it.
So in a code that looks like:
A a = new A();
a.setSomething( new B() {
public void bMethod() {
// Run stuff
}
} );
C c = a.getSomething();
The "Run stuff" part is not ran now. An object is created, with a method that can be used later inside it, and that object is passed into a. The method is not going to run until something specifically calls it. When you get to the getSomething(), the "Run stuff" part has not run.
So in your code:
JComboBox occupancy_list = new JComboBox(occupancy_string);
occupancy_list.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent event)//Listener for Occupancy Drop Down
{
JComboBox cb = (JComboBox)event.getSource(); //grab the user selection
String selection = (String) cb.getSelectedItem();
int number = Integer.parseInt((String) selection);
}
});
String selection = (String) occupancy_list.getSelectedItem();
You create the occupancy list, you create an action listener for it, and store that action listener inside your occupancy list. But none of the stuff written inside the actionPerformed() method is going to run until the GUI is displayed, the user selects something, and the event is fired.
GUI programming is different than console programming where you call "scan()" and then the program just stops and waits for something to be entered. You first prepare the GUI, and when you display it, the various listeners are called based on what the user does.
So your code jumps straight to the occupancy_list.getSelectedItem() before the list has even been added to the GUI, and of course, nothing is selected, nothing is displayed, yet, so the other drop-down lists are created way before the user even sees the GUI.
This is true for all the action listeners in the code.
The proper way to write an action listener is to think what will be the conditions when the GUI is already running. Your action listeners merely set values in local variables that are going to be discarded. Instead, they should do the things that you want to do when the user makes a selection, right inside the action listener.
This means that the action listener for this combo box will have to create the other lists and add them to the GUI, revalidate and repaint it. Or it may simply modify the other lists which will be created already, depending on what you think is best. But they will have to access those lists, and therefore the lists have to be defined as fields of the surrounding class, and accessed inside the action listener. Note that you can also define a method that does this and call it from inside the action listener.
My suggestion would be to create a simple GUI first with just the first combo box and make it change something simple based on the selection. You can follow the Oracle Tutorial, for example. After you understand how to write an action listener that changes something simple, expand your program to add the other lists and manipulate them from the action listener.

How to bind different listener to different ScrollPane

I have a class that defines a graphical interface with two JList. For each JList I would like to associate a method public void valueChanged(ListSelectionEvent s) but I can't do it (obviously). So how can I fix it?
This is my code:
public class Inbox implements ListSelectionListener {
public static void main(String[] args) {
Inbox inbox = new Inbox();
}
JFrame frame = new JFrame();
JPanel panel = new JPanel();
JPanel titlePanel = new JPanel();
JPanel centerPanel = new JPanel();
JPanel listPanel = new JPanel();
JPanel listRicPanel = new JPanel();
JPanel listInvPanel = new JPanel();
JPanel messPanel = new JPanel();
JPanel buttonPanel = new JPanel();
GridBagConstraints c;
JButton indietro = new JButton("Indietro");
JButton ok = new JButton("Ok");
String ricevuti[] = {"1", "2", "3", "4", "5", "6", "7", "8", "9"};
JList ricList = new JList(ricevuti);
String inviati[] = {"A", "B", "C", "D", "E"};
JList invList = new JList(inviati);
Inbox() {
frame.setTitle("Inbox"); //nome della finestra (frame)
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(panel);
frame.setVisible(true);
panel.setLayout(new BorderLayout());
centerPanel.setLayout(new BorderLayout());
listPanel.setLayout(new GridLayout(2, 0));
panel.add(titlePanel, BorderLayout.NORTH);
panel.add(buttonPanel, BorderLayout.SOUTH);
panel.add(centerPanel, BorderLayout.CENTER);
buttonPanel.add(indietro);
buttonPanel.add(ok);
centerPanel.add(listPanel, BorderLayout.WEST);
centerPanel.add(messPanel, BorderLayout.CENTER);
listPanel.add(listRicPanel);
listPanel.add(listInvPanel);
/** ScrollPane containing the first list **/
ricList.setVisibleRowCount(10);
ricList.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
listRicPanel.add(new JScrollPane(ricList));
ricList.addListSelectionListener(this);
/** ScrollPane containing the second list **/
invList.setVisibleRowCount(10);
invList.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
listInvPanel.add(new JScrollPane(invList));
invList.addListSelectionListener(this);
frame.pack();
}
/**
* First listener.
*/
public void valueChanged(ListSelectionEvent e) {
String str = (String) ricList.getSelectedValue();
if(str.equals("Alex"))
System.out.println("Alex");
else if(str.equals("John"))
System.out.println("John");
else
System.out.println("Other name");
}
/**
* Second listener.
*/
public void valueChanged(ListSelectionEvent e) {
String str = (String) invList.getSelectedValue();
if(str.equals("Alex"))
System.out.println("Alex");
else if(str.equals("John"))
System.out.println("John");
else
System.out.println("Other name");
}
}
I wish the program would combine different listeners to different scroolPane, as I do that?
Thank you very much!

It must be one method but you can use e.getSource() method to get JList instance which fires the event. Then you can use it like this
public void valueChanged(ListSelectionEvent e) {
String str = (String) ((JList)e.getSource()).getSelectedValue();
if(str.equals("Alex"))
System.out.println("Alex");
else if(str.equals("John"))
System.out.println("John");
else
System.out.println("Other name");
}
Of course the listener must be added to both list instances

You Could
Determine the source of the event and branch your logic based on the result...
public void valueChanged(ListSelectionEvent e) {
if (e.getSource() == ricList) {
//...
else if (e.getSource() == invList) {
//...
}
}
This assumes that you want to perform different logic for each source. This can become a little cumbersome if you have more than a few possible sources...
Instead of "implementing" ListSelectionListener at the class level...
You Could...
Define a completely external class that does the specific job you want...
public class MyListSelectionListener implements ListSelectionListener {
public void valueChanged(ListSelectionEvent s) {
// Custom job here...
}
}
This can be a good and bad thing depending on your needs...One problem with this is you may be required to provide additional context to the class in order for it to perform it's operations, as the event object may not provide enough context alone
You Could
Create inner classes that do a specific job, in particular for the class they've been defined within...
public class Inbox {
//...
Inbox() {
//...
ricList.addListSelectionListener(new RicListSelectionListener());
//...
invList.addListSelectionListener(new InvListSelectionListener());
}
//...
public class RicListSelectionListener implements ListSelectionListener {
public void valueChanged(ListSelectionEvent s) {
String str = (String) ricList.getSelectedValue();
if(str.equals("Alex"))
System.out.println("Alex");
else if(str.equals("John"))
System.out.println("John");
else
System.out.println("Other name");
}
}
public class InvListSelectionListener implements ListSelectionListener {
public void valueChanged(ListSelectionEvent s) {
String str = (String) invList.getSelectedValue();
if(str.equals("Alex"))
System.out.println("Alex");
else if(str.equals("John"))
System.out.println("John");
else
System.out.println("Other name");
}
}
}
The nice thing about this is the classes have access to all the instance variables and methods within the parent class and are neat and tidy and easy to find when you need...
Take a look at Inner Class Example for more details
You Could...
Use anonymous classes. These are a little like inner classes, except they are defined in line...
public class Inbox {
//...
Inbox() {
//...
ricList.addListSelectionListener(new ListSelectionListener {
public void valueChanged(ListSelectionEvent s) {
String str = (String) ricList.getSelectedValue();
if(str.equals("Alex"))
System.out.println("Alex");
else if(str.equals("John"))
System.out.println("John");
else
System.out.println("Other name");
}
});
//...
invList.addListSelectionListener(new ListSelectionListener() {
public void valueChanged(ListSelectionEvent s) {
String str = (String) invList.getSelectedValue();
if(str.equals("Alex"))
System.out.println("Alex");
else if(str.equals("John"))
System.out.println("John");
else
System.out.println("Other name");
}
});
}
}
These can clutter the code if they are too long and should be used sparingly for that reason, but are really good for plumbing together existing functionality.
Take a look at Anonymous Classes for more details

multiple JComboBox in one JPanel

I have a JPanel with three JComboBox. Here is the code I wrote:
public class Main {
private static String pat_order;
private static String PS_selection;
private static String ovlp_selection;
public static void main(String args[]) throws FileNotFoundException, IOException {
Date start_time = new Date();
try {
GridBagConstraints gbc = new GridBagConstraints();
final JComboBox jc = new JComboBox();
jc.addItem("ARR");
jc.addItem("SRR");
final JComboBox jc1 = new JComboBox();
jc1.addItem("RR");
jc1.addItem("IQC");
final JComboBox jc2 = new JComboBox();
jc2.addItem("YES");
jc2.addItem("NO");
JPanel myPanel = new JPanel(new GridBagLayout());
myPanel.add(jc, gbc);
myPanel.add(jc1, gbc);
myPanel.add(jc2, gbc);
jc.addItemListener(new ItemListener() {
public void itemStateChanged(ItemEvent ie) {
String order = (String) jc.getSelectedItem();
pat_order = order;
}
});
jc1.addItemListener(new ItemListener() {
public void itemStateChanged(ItemEvent ie) {
String PS_method = (String) jc1.getSelectedItem();
PS_selection = PS_method;
}
});
jc2.addItemListener(new ItemListener() {
public void itemStateChanged(ItemEvent ie) {
String ovlp_user = (String) jc2.getSelectedItem();
ovlp_selection = ovlp_user;
}
});
if (pat_order == "ARR") {
Arrays.sort(patterns_array, new ColumnComparator(0));
} else if (pat_order == "SRR") {
Arrays.sort(patterns_array, new ColumnComparator(1));
}
if (PS_selection == "RR") {
System.out.println("RR");
} else if (PS_selection == "IQC") {
System.out.println("IQC");
}
if (ovlp_selection == "YES") {
Overlap a = new Overlap(Xdisc, final_patterns, k, Yresid, Xresid, projectname, pat_order, PS_selection);
}
} catch (Exception e) {
System.err.println("Error: " + e.getMessage());
} finally {
}
}
}
The problem is that the first JComboBox is working fine, but the second and third is doing nothing. It would be great if you can help me in this problem.

You seem to be running your UI as if it was a console program. UI's don't work this way, they respond to events. These events may come in any order and at any time...
Dialogs are a great way of control the flow of the execution. They will block code until the dialog is closed, allowing you to ascertain the results and take appropriate action.
Take a look at How to use dialogs for more details...
While you there, you might also want to take a look through Creating a UI with Swing which will explain more of the concepts you need to understand.
Like the fact that a UI needs some kind of Window in order to be displayed on the screen

Try to add ActionListener instead of ItemListener

Java Swing Combobox removeAllItems calling ItemStateChanged also?

My code is quite simple actually. I saw a simple and similar code was from this article.
At first, I have 1 combobox. I have a listener on it called itemStateChanged(). My purpose to add into this listener is that; "to execute some code when user click (select) an item from its dropbox".
Cmb_ItemCategory = new javax.swing.JComboBox();
Cmb_ItemCategory.setModel(new javax.swing.DefaultComboBoxModel(new String[] { "Loading..." }));
Cmb_ItemCategory.addItemListener(new java.awt.event.ItemListener() {
public void itemStateChanged(java.awt.event.ItemEvent evt) {
Cmb_ItemCategoryItemStateChanged(evt);
}
});
private void Cmb_ItemCategoryItemStateChanged(java.awt.event.ItemEvent evt) {
if(evt.getStateChange() == java.awt.event.ItemEvent.SELECTED){
System.err.println("Sombody click or change my model content");
}
}
Behind the code, I grab some data, and then calling a method of removeAllItems() .
And then I set a new Model (from new data) into it.
-- at another line of code ---
Cmb_ItemCategory.removeAllItems();
Cmb_ItemCategory.setModel(newModel);
I juz realized that my itemStateChanged() is called when i do the removeAllItem() method. called once.
So, How to make it only called once user Click (select) only AND not when removeAllItems() called?
it similar to this article. But it's not removingItems case. CMIIW.

Here check this code out, this works flawlessly, might be you doing something wrong where you calling removeAllItems() :
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class ComboState
{
private void createAndDisplayGUI()
{
JFrame frame = new JFrame("Combo State Testing : ");
frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
final JComboBox cbox = new JComboBox();
cbox.addItem("One");
cbox.addItem("Two");
cbox.addItem("Three");
cbox.addItem("Four");
cbox.addItemListener(new ItemListener()
{
public void itemStateChanged(ItemEvent ie)
{
if (ie.getStateChange() == ItemEvent.SELECTED)
{
System.out.println("Item Selected is : " + ie.getItem());
}
/*else
{
System.out.println("I am called for other reasons.");
}*/
}
});
/*
* Click me to remove JComboBox's items.
*/
JButton removeButton = new JButton("REMOVE");
removeButton.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent ae)
{
cbox.removeAllItems();
}
});
frame.add(cbox, BorderLayout.CENTER);
frame.add(removeButton, BorderLayout.PAGE_END);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
public static void main(String... args)
{
SwingUtilities.invokeLater(new Runnable()
{
public void run()
{
new ComboState().createAndDisplayGUI();
}
});
}
}

As nIcE cOw already illustrated in his example, it should certainly work when you use a DefaultComboBoxModel (which is the case in his sample code, although it happens behind the screens).
I could explain the behavior you encounter for the non-DefaultComboBoxModel case, although your code snippet suggests you use one. Looking at the source code for JComboBox#removeAllItems there is a different code path since the removeAllElements method is not part of the MutableComboBoxModel interface
public void removeAllItems() {
checkMutableComboBoxModel();
MutableComboBoxModel<E> model = (MutableComboBoxModel<E>)dataModel;
int size = model.getSize();
if ( model instanceof DefaultComboBoxModel ) {
((DefaultComboBoxModel)model).removeAllElements();
}
else {
for ( int i = 0; i < size; ++i ) {
E element = model.getElementAt( 0 );
model.removeElement( element );
}
}
selectedItemReminder = null;
if (isEditable()) {
editor.setItem(null);
}
}
So with a non-DefaultComboBoxModel you are going to remove the items one by one. This means that at a certain point in time, you will remove the selected element. A possible implementation of your model might change the selected element at that point. If you look for example at the implementation in DefaultComboBoxModel (although this code will not be triggered) you can clearly see it changes the selection.
public void removeElementAt(int index) {
if ( getElementAt( index ) == selectedObject ) {
if ( index == 0 ) {
setSelectedItem( getSize() == 1 ? null : getElementAt( index + 1 ) );
}
else {
setSelectedItem( getElementAt( index - 1 ) );
}
}
objects.removeElementAt(index);
fireIntervalRemoved(this, index, index);
}
Perhaps your model does something similar, which explains the event. Just for making this post complete, the code behind the DefaultComboBoxModel#removeAllElements where you can clearly see it sets the selection to null and does not select another object. Only weird thing in that code is that it does not fire a DESELECTED event first, although you know the selection has changed if you listen for the intervalRemoved event ... but that is not really relevant to your problem
public void removeAllElements() {
if ( objects.size() > 0 ) {
int firstIndex = 0;
int lastIndex = objects.size() - 1;
objects.removeAllElements();
selectedObject = null;
fireIntervalRemoved(this, firstIndex, lastIndex);
} else {
selectedObject = null;
}
}
So to conclude: I say the solution for your problem is located in your model, and not in the code you posted

One quick way to do is to have a bool set to true before you call removeAllItem() and back false after. Execute the code in your itemStateChanged() only if the bool variable is false.
Ideally you could override the removeAllItem() function.

not clear from whole discusion,
you have to remove all Listener(s) from JComboBox before removing all Items, after Items are removed you can add Listener(s) back,
still not sure if you want to add & remove Items dynamically, or you can set whatever value for another JComponent(s),
(against complicating simple things) did you see there remove,
.
import java.awt.*;
import java.awt.event.*;
import java.util.*;
import javax.swing.*;
public class ComboBoxTwo extends JFrame implements ActionListener, ItemListener {
private static final long serialVersionUID = 1L;
private JComboBox mainComboBox;
private JComboBox subComboBox;
private Hashtable<Object, Object> subItems = new Hashtable<Object, Object>();
public ComboBoxTwo() {
String[] items = {"Select Item", "Color", "Shape", "Fruit"};
mainComboBox = new JComboBox(items);
mainComboBox.addActionListener(this);
mainComboBox.addItemListener(this);
//prevent action events from being fired when the up/down arrow keys are used
//mainComboBox.putClientProperty("JComboBox.isTableCellEditor", Boolean.TRUE);
getContentPane().add(mainComboBox, BorderLayout.WEST);
subComboBox = new JComboBox();// Create sub combo box with multiple models
subComboBox.setPrototypeDisplayValue("XXXXXXXXXX"); // JDK1.4
subComboBox.addItemListener(this);
getContentPane().add(subComboBox, BorderLayout.EAST);
String[] subItems1 = {"Select Color", "Red", "Blue", "Green"};
subItems.put(items[1], subItems1);
String[] subItems2 = {"Select Shape", "Circle", "Square", "Triangle"};
subItems.put(items[2], subItems2);
String[] subItems3 = {"Select Fruit", "Apple", "Orange", "Banana"};
subItems.put(items[3], subItems3);
// mainComboBox.setSelectedIndex(1);
}
#Override
public void actionPerformed(ActionEvent e) {
String item = (String) mainComboBox.getSelectedItem();
Object o = subItems.get(item);
if (o == null) {
subComboBox.setModel(new DefaultComboBoxModel());
} else {
subComboBox.setModel(new DefaultComboBoxModel((String[]) o));
}
}
#Override
public void itemStateChanged(ItemEvent e) {
if (e.getStateChange() == ItemEvent.SELECTED) {
if (e.getSource() == mainComboBox) {
if (mainComboBox.getSelectedIndex() != 0) {
FirstDialog firstDialog = new FirstDialog(ComboBoxTwo.this,
mainComboBox.getSelectedItem().toString(), "Please wait, Searching for ..... ");
}
}
}
}
private class FirstDialog extends JDialog {
private static final long serialVersionUID = 1L;
FirstDialog(final Frame parent, String winTitle, String msgString) {
super(parent, winTitle);
setModalityType(Dialog.ModalityType.APPLICATION_MODAL);
JLabel myLabel = new JLabel(msgString);
JButton bNext = new JButton("Stop Processes");
add(myLabel, BorderLayout.CENTER);
add(bNext, BorderLayout.SOUTH);
bNext.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent evt) {
setVisible(false);
}
});
javax.swing.Timer t = new javax.swing.Timer(1000, new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
setVisible(false);
}
});
t.setRepeats(false);
t.start();
setLocationRelativeTo(parent);
setSize(new Dimension(400, 100));
setVisible(true);
}
}
public static void main(String[] args) {
JFrame frame = new ComboBoxTwo();
frame.setDefaultCloseOperation(EXIT_ON_CLOSE);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
}

The method removeAllItems does not call ItemStateChanged, but it call actionPerformed, you can check it by running this simple code:
public class Tuto {
public static void main(String[] args) {
//create the main frame
JFrame frame = new JFrame();
frame.setResizable(false);
frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
frame.setLayout(null);
frame.setLocation(new Point(10, 10));
frame.setPreferredSize(new Dimension(400, 300));
JComboBox<String> combo = new JComboBox();
combo.addItem("item 1");
combo.addItem("item 2");
combo.addItem("item 3");
combo.setBounds(50, 30, 300, 20);
combo.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent ae) {
System.out.println(" action Performed ");
}
});
frame.add(combo);
JButton button = new JButton("Remove");
button.setBounds(50, 100, 100, 30);
button.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent ae) {
combo.removeAllItems();
}
});
frame.add(button);
frame.pack();
frame.setVisible(true);
}
}