JList update

Question

Hi,
I have a JList, for which I have a set of data represented as a queue, now, everytime I change the queue I fire an event to tell the list to update itself.., but the list won't.
I have tried validate, revalidate and a few others, but so far the only way of doing this that I have been able to work with is:
     * This gets called when the queue is updated in order to update the display
     *@param ch The type of the change, one of CH_POP, CH_PUT or CH_PUSH
     *@param inx The index of the change
     *@param o The object put or removed to/from the queue
    private void change(int ch, int inx, Object o){
        queueList.setModel(new AbstractListModel() {
            public int getSize() {
                return qc.size();    // qc = the queue object
            public Object getElementAt(int i) {
                return qc.peek(i);
    }Anyone know a better way of doing this?
thanks,
david

Answer 1

Here is one way of doing it. You just need to substitute your Queue implementation for the ArrayList.
Or you could have your Queue extend AbstractListModel. Anyway...
import javax.swing.*;
import javax.swing.event.*;
import javax.swing.table.*;
import java.util.ArrayList;
import java.beans.PropertyChangeListener;
import java.beans.PropertyChangeEvent;
import java.awt.*;
import java.awt.event.*;
public class QueueList extends JFrame implements ActionListener
    Point point1 = new Point(10,10);
    Point point2 = new Point(10,10);
    Point point3 = new Point(10,10);
    Point point4 = new Point(10,10);
    JButton add, remove;
    ArrayListModel dataModel;
    int counter = 1;
    public QueueList()
        super( "Array*(Queue)  List Demo");
        setDefaultCloseOperation( EXIT_ON_CLOSE );
        Container content = getContentPane();
        ArrayList dataList = new ArrayList();
        for( int i = 0; i < 10; i++ )
            dataList.add( ""+counter++ );
        JList list = new JList( dataModel = new ArrayListModel( dataList ) );
        JPanel panel = new JPanel();
        panel.add( add = new JButton("Add") );
        add.addActionListener( this );
        panel.add( remove = new JButton("Remove") );
        remove.addActionListener( this );
        content.add( new JScrollPane( list ), BorderLayout.CENTER );
        content.add(panel, BorderLayout.SOUTH );
        pack();
        show();
    public static void main(String[] args)
        try
            UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
        catch( Exception e )
        new QueueList();
     * Invoked when an action occurs.
    public void actionPerformed(ActionEvent e)
        if( e.getSource().equals( add ) )
            dataModel.add( ""+counter++);
        else if( e.getSource().equals( remove ) )
            dataModel.remove(0);
    public class ArrayListModel extends AbstractListModel
        ArrayList arrayList;
        public ArrayListModel( ArrayList arrayList )
            this.arrayList = arrayList;
        public int getSize()
            return( arrayList.size() );
         * Returns the value at the specified index.
         * @param index the requested index
         * @return the value at <code>index</code>
        public Object getElementAt(int index)
            return( arrayList.get(index) );
        public void add( Object obj )
            arrayList.add( obj );
            fireContentsChanged(this, this.getSize(),this.getSize());
        public void remove( int index )
            if( arrayList.size() > 0 )
                arrayList.remove(index);
                fireContentsChanged(this,0,0);
}