JComboBox items not showing up properly ?

Question

I have the following program :
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
import java.util.*;
public class Java_Test extends JPanel
  static JTabbedPane Tabbed_Pane=new JTabbedPane();
  JComboBox Contacts_ComboBox;
  Customer_Info_Panel A_Customer_Info_Panel=new Customer_Info_Panel();
  Java_Test()
    JPanel A_Tab_Panel=new JPanel();
    A_Tab_Panel.setPreferredSize(new Dimension(300,200));
    A_Tab_Panel.add(A_Customer_Info_Panel);
    JPanel B_Tab_Panel=new JPanel();
    B_Tab_Panel.setPreferredSize(new Dimension(300,200));
    Contacts_ComboBox=new JComboBox(A_Customer_Info_Panel.Contacts_Id_Vector);
//    Contacts_ComboBox=new JComboBox(A_Customer_Info_Panel.Contacts_Id_ComboBox.getModel());
    Contacts_ComboBox.setMaximumRowCount(30);
    Contacts_ComboBox.setSelectedIndex(-1);
    Contacts_ComboBox.setPreferredSize(new Dimension(129,22));
    B_Tab_Panel.add(new JLabel("Select Customer Info From List :"));
    B_Tab_Panel.add(Contacts_ComboBox);
    Tabbed_Pane.addTab("A : Enter Customer Info",null,A_Tab_Panel,null);
    Tabbed_Pane.addTab("B : Use Entered Info",null,B_Tab_Panel,null);
    add(Tabbed_Pane);
    setPreferredSize(new Dimension(500,300));
  static void Out(String message) { System.out.println(message); }   
  public static void main(String[] args)
    final Java_Test demo=new Java_Test();
    Dimension Screen_Size=Toolkit.getDefaultToolkit().getScreenSize();
    final JFrame frame=new JFrame("JComboBox Test");
    frame.add(demo);
    frame.addWindowListener(new WindowAdapter()
      public void windowClosing(WindowEvent e)  { System.exit(0); }
      public void windowDeiconified(WindowEvent e)  { demo.repaint(); }
      public void windowGainedFocus(WindowEvent e)  { demo.repaint(); }
      public void windowOpening(WindowEvent e) { demo.repaint(); }
      public void windowResized(WindowEvent e) { demo.repaint(); } 
      public void windowStateChanged(WindowEvent e) { demo.repaint(); }
    frame.pack();
    frame.setBounds((Screen_Size.width-demo.getWidth())/2,(Screen_Size.height-demo.getHeight())/2-10,demo.getWidth(),demo.getHeight()+38);
    frame.setVisible(true);
class Customer_Info_Panel extends JPanel
  Vector<String> Contacts_Id_Vector=new Vector<String>();
  JComboBox Contacts_Id_ComboBox=new JComboBox(Contacts_Id_Vector);
  Customer_Info_Panel()
    Contacts_Id_ComboBox=new JComboBox(Contacts_Id_Vector);
    Contacts_Id_ComboBox.setMaximumRowCount(30);
    Contacts_Id_ComboBox.setSelectedIndex(-1);
    Contacts_Id_ComboBox.setEditable(true);
    Contacts_Id_ComboBox.setPreferredSize(new Dimension(129,22));
    Contacts_Id_ComboBox.addActionListener(new ActionListener()
      public void actionPerformed(ActionEvent evt)
        String New_Item=Contacts_Id_ComboBox.getSelectedItem()==null?"":Contacts_Id_ComboBox.getSelectedItem().toString().trim();
        if (!Contacts_Id_Vector.contains(New_Item)) Contacts_Id_Vector.add(New_Item);
//        Contacts_Id_ComboBox.firePopupMenuWillBecomeVisible();
    add(new JLabel("Please Enter Customer Info Below :"));
    add(Contacts_Id_ComboBox);
    setPreferredSize(new Dimension(270,170));
}It complies and demonstrates the problem detailed below :
<1> In Tab A, enter "123" into the JComboBox and hit the "Enter" key, now I have one item in the drop down list
<2> In Tab A again, enter "ABC" and hit the "Enter" key again, now I have both "123" and "ABC" in Tab A's drop down list
<3> Now in Tab B you can see both items you entered in Tab A, try select one of them, it seems to work fine
<4> Goto Tab A and enter "111" and hit the "Enter" key, now if you click on the drop down list, they are all gone, you can't see any of them, but if you look at Tab B, they are all there, sometimes Tab B shows an empty list, but if you click in the empty list, they will show up correctly. But in Tab A no matter how you click, you can't see any item.
I tried to enter all three items in Tab A one after another : 123[Enter key] + ABC[Enter key] + 111[Enter key] then look them up in Tab B, they are all there, but if I go back to Tab A and try to enter "333"+[Enter key], all items in A will be gone again.
I found this problem a year ago, but I am now running Java 1.6.0_03 on Windows XP, the problem is still there.
Maybe it's my program's problem, but how to fix it ? I need a JComboBox in Tab A that user can enter info and in Tab B I need another JComboBox that user can use the entered info from Tab A, any time the info in Tab A gets changed, it needs to be reflected in Tab B's JComboBox, am I doing it the wrong way ? If so, what's the right way ?
The above program will compile and run to show you the problem.
Frank

Answer 1

petes1234, I tried your program, it works great, exactly as I expected, I also tried to add a delete button next to the check button, it can delete items in Tab A, but not in Tab B or C, works correctly, because only in Tab A do I expect users to modify data, the data in Tab B is read only, so this satisfies my needs, the modifies program looks like this now :
import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.Vector;
import javax.swing.BorderFactory;
import javax.swing.ComboBoxModel;
import javax.swing.DefaultComboBoxModel;
import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTabbedPane;
import javax.swing.MutableComboBoxModel;
public class ComboFoo extends JPanel
    private static final int MAX_ROW_COUNT = 30;
    private JComboBox comboA;
    private JComboBox comboB;
    private JComboBox comboC;
//    private Vector<String> sharedComboData;
    MutableComboBoxModel sharedComboData;
    public ComboFoo()
        int ebGap = 8;
        int glGap = 5;
        setBorder(BorderFactory.createEmptyBorder(ebGap, ebGap, ebGap, ebGap));
        setLayout(new GridLayout(0, 1, glGap, glGap));
        JTabbedPane tabbedPane = new JTabbedPane();
        tabbedPane.setPreferredSize(new Dimension(300, 200));
        add(tabbedPane);
        //sharedComboData = new Vector<String>();
        sharedComboData = new DefaultComboBoxModel();
        comboA = new JComboBox(sharedComboData);
        comboB = new JComboBox(sharedComboData);
        comboC = new JComboBox(sharedComboData);
        comboA.setEditable(true);
        comboB.setEditable(false);
        comboC.setEditable(false);
        comboA.setMaximumRowCount(MAX_ROW_COUNT);
        comboA.setSelectedIndex(-1);
        comboA.addActionListener(new ActionListener()
            public void actionPerformed(ActionEvent event)
            {   comboAAction(event); }
        tabbedPane.addTab("Tab A", createPanel(comboA, "Master ComboBox: comboA"));
        tabbedPane.addTab("Tab B", createPanel(comboB, "Slave ComboBox: comboB"));
        JPanel lowerPanel = createPanel(comboC, "Slave ComboBox: comboC");
        add(lowerPanel);
    private void comboAAction(ActionEvent event)
        String newItem = (String)comboA.getSelectedItem();
        newItem = (newItem == null) ? "" : newItem.trim();
        MutableComboBoxModel comboAModel = (MutableComboBoxModel)comboA.getModel();
        int comboAModelSize = comboAModel.getSize();
        boolean hasItem = false;
        for (int i = 0; i < comboAModelSize; i++)
            if (newItem.equals(comboAModel.getElementAt(i)))
                hasItem = true;
        if (!hasItem)
            comboAModel.addElement(newItem);
        if (!sharedComboData.contains(newItem))
            sharedComboData.add(newItem);
        //sharedComboData.addElement(newItem);
    private JPanel createPanel(JComboBox combo, String text)
        JPanel comboPanel = new JPanel(new BorderLayout());
        int ebGap = 10;
        comboPanel.setBorder(BorderFactory.createEmptyBorder(ebGap, ebGap, ebGap, ebGap));
        comboPanel.add(combo, BorderLayout.NORTH);
        final JComboBox jpCombo = combo; // so I can check in actionlistener
        comboPanel.add(new JLabel(text), BorderLayout.CENTER);
        // checks the contents and state of the current combobox
        // and prints the information in the Console.
        JPanel btnPanel = new JPanel();
        JButton checkComboBtn = new JButton("Check Combo");
        checkComboBtn.addActionListener(new ActionListener()
            public void actionPerformed(ActionEvent event)
                if (jpCombo == comboA)
                    System.out.println("comboA");
                else if (jpCombo == comboB)
                    System.out.println("comboB");
                else if (jpCombo == comboC)
                    System.out.println("comboC");
                int itemCount = jpCombo.getItemCount();
                System.out.println("item count = " + itemCount);
                System.out.println("selected index = " + jpCombo.getSelectedIndex());
                System.out.println("selected item = " + jpCombo.getSelectedItem());
                System.out.println("List Items:");
                for (int i = 0; i < itemCount; i++)
                    System.out.println("  " + jpCombo.getItemAt(i).toString());
                System.out.println();
        btnPanel.add(checkComboBtn);
        JButton deleteComboBtn = new JButton("Delete Item");
        deleteComboBtn.addActionListener(new ActionListener()
            public void actionPerformed(ActionEvent event)
                if (jpCombo == comboA)
                    System.out.println("comboA");
                    sharedComboData.removeElementAt(jpCombo.getSelectedIndex());
                else if (jpCombo == comboB)
                    System.out.println("comboB");
                else if (jpCombo == comboC)
                    System.out.println("comboC");
                int itemCount = jpCombo.getItemCount();
                System.out.println("item count = " + itemCount);
                System.out.println("selected index = " + jpCombo.getSelectedIndex());
                System.out.println("selected item = " + jpCombo.getSelectedItem());
                System.out.println("List Items:");
                for (int i = 0; i < itemCount; i++)
                    System.out.println("  " + jpCombo.getItemAt(i).toString());
                System.out.println();
        btnPanel.add(deleteComboBtn);
        comboPanel.add(btnPanel, BorderLayout.SOUTH);
        return comboPanel;
    private static void createAndShowGUI()
        JFrame frame = new JFrame("ComboFoo Application");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.getContentPane().add(new ComboFoo());
        frame.setLocationRelativeTo(null);
        frame.pack();
        frame.setVisible(true);
    public static void main(String[] args)
        javax.swing.SwingUtilities.invokeLater(new Runnable()
            public void run()
                createAndShowGUI();
}Thanks petes1234 for the help ! But is there a down side for using MutableComboBoxModel instead of Vector, such as "thread safe" issue ? When is MutableComboBoxModel more suitable than Vector and vise versa ? Especially in this situation.