Q: AbstractComboBoxModel and AbstractListModel

Question

This post replaces one that was summarily executed... (religious content?)
mlk had told me not to use DefaultComoboBoxModel, but to use ComboBoxModel and AbstractList model instead to build a dynamically updatable combo box. Here is the response I was writing but was unable to post to the missing thread.
Using DefaultComboBoxModel wast the "hit it with a bigger hammer" approach.
In my Googling of the copious resources I found references to ComboBoxModel, AbstractComboBoxModel, and noticed with some consternation that I was supposed to understand something called an AbstractListModel. However, I could find no useful examples or tutorials on these classes (just the same old API docs over and over and over...) which is why, in desperation, I posted here in the first place.
If you can provide me with a coherant, concise example of how to make a combo box that is dynamically updatable without blowing away a DefaultComboBoxModel instance and replacing it every time, I will be very grateful. I have a 1500 page college text on Java with nothing pertinent in it.
YAT and walker;
Its a pleasure to associate with people who obviously are students of religious history and philosophy. Sadly I guess the discussion wasn't politically correct. So let's talk about combo boxes.

Answer 1

// Write your own documentation. It's not too complicated.
import java.util.*;
import javax.swing.*;
import javax.swing.event.*;
public class RefreshableComboBoxModel extends DefaultComboBoxModel
    private boolean notify = true;
    private final Set<ListDataListener> listeners =
                                                new HashSet<ListDataListener>();
        super.addListDataListener(
            new ListDataListener()
                public void contentsChanged(ListDataEvent evt)
                    if (notify)
                        notifyContentsChanged(evt);
                public void intervalAdded(ListDataEvent evt)
                    if (notify)
                        notifyIntervalAdded(evt);
                public void intervalRemoved(ListDataEvent evt)
                    if (notify)
                        notifyIntervalRemoved(evt);
    public void addListDataListener(ListDataListener ldl)
        listeners.add(ldl);
    public void removeListDataListener(ListDataListener ldl)
        listeners.remove(ldl);
    private void notifyContentsChanged(ListDataEvent evt)
        for (ListDataListener ldl : listeners)
            ldl.contentsChanged(evt);
    private void notifyIntervalAdded(ListDataEvent evt)
        for (ListDataListener ldl : listeners)
            ldl.intervalAdded(evt);
    private void notifyIntervalRemoved(ListDataEvent evt)
        for (ListDataListener ldl : listeners)
            ldl.intervalRemoved(evt);
    public void updateContents(List<?> newContents)
        notify = false;
        int count = getSize();
        removeAllElements();
        for (Object obj : newContents)
            addElement(obj);
        int size = getSize();
        notify = true;
        if (count > 0 || size > 0)
            // Assume the contents have changed. Therefore we need to fire an
            // event. It's easiest to make it CONTENTS_CHANGED rather than to
            // try to track whether we have merely added or removed elements.
            // The upper index is the greater of (count - 1) and (size - 1),
            // as it is inclusive.
            fireContentsChanged(ListDataEvent.CONTENTS_CHANGED,
                                0,
                                Math.max(count, size) - 1);
        // Up to you whether or not to check the status wrt the selected
        // element.
import java.awt.*;
import java.awt.event.*;
import java.util.*;
import javax.swing.*;
public class RefreshableComboBoxModelTest
    public static void main(String[] args)
        JFrame jf = new JFrame("Testing the RefreshableComboBoxModel");
        JPanel jp = new JPanel();
        jf.getContentPane().add(jp);
        JPanel left = new JPanel();
        final JTextField jtf = new JTextField();
        JButton add = new JButton("Add");
        JButton remove = new JButton("Remove");
        final DefaultListModel lm = new DefaultListModel();
        final JList jl = new JList(lm);
        lm.addElement("Foo");
        left.setLayout(new GridBagLayout());
        GridBagConstraints gbc = new GridBagConstraints();
        gbc.gridx = 0;
        gbc.fill = gbc.HORIZONTAL;
        left.add(jtf, gbc);
        left.add(add, gbc);
        left.add(remove, gbc);
        gbc.fill = gbc.BOTH;
        left.add(jl, gbc);
        add.addActionListener(
            new ActionListener()
                public void actionPerformed(ActionEvent evt)
                    String str = jtf.getText();
                    if (str != null && str.length() > 0)
                        lm.addElement(str);
        remove.addActionListener(
            new ActionListener()
                public void actionPerformed(ActionEvent evt)
                    int[] sel = jl.getSelectedIndices();
                    for (int i = sel.length - 1; i >= 0; i--)
                        lm.removeElementAt(sel);
jp.setLayout(new GridBagLayout());
gbc.gridx = gbc.RELATIVE;
gbc.gridy = 0;
gbc.weightx = 1;
jp.add(left, gbc);
JPanel middle = new JPanel();
JButton update = new JButton("->");
middle.add(update);
jp.add(middle, gbc);
JPanel right = new JPanel();
right.setLayout(new GridBagLayout());
final RefreshableComboBoxModel cbm = new RefreshableComboBoxModel();
right.add(new JComboBox(cbm), gbc);
jp.add(right, gbc);
update.addActionListener(
new ActionListener()
public void actionPerformed(ActionEvent evt)
java.util.List<Object> elts = new ArrayList<Object>();
Enumeration<?> enumn = lm.elements();
while (enumn.hasMoreElements())
elts.add(enumn.nextElement());
cbm.updateContents(elts);
jf.pack();
jf.setVisible(true);
jf.setDefaultCloseOperation(jf.EXIT_ON_CLOSE);