Model in my JList not reflecting the new value I added to it?

Question

uness I create a new model object and modify it then my code does not work as I want. Adding new data to the exitsting model causes the JList to display blank when I refresh the screen. I have created my own implementation of an editable Model.
When my action performed creates a new instance of the model everything works fine but is this how it should work?
//In my GUI I have a JList initialized with the model ....
private EditableListModel model = new EditableListModel();
model.add("one");
model.add("two");
model.add("three");
colsToDisplayJList.setModel( model );
I have a button with the following action performed
    private void addActionPerformed(java.awt.event.ActionEvent evt) {                                   
        //model = new EditableListModel();
        model.add("four");
        colsToDisplayJList.setModel( model );
//EditableModel implementation
import java.util.*;
import javax.swing.AbstractListModel;
public class EditableListModel extends AbstractListModel
    private Vector items = new Vector();
    public Object getElementAt(int key)
        return items.get( key );
    public int getSize()
        return items.size();
    public void add( String item )
        items.add( item );
    public void remove( String key )
        Iterator iter =  items.iterator();
        int index = 0;
        while( iter.hasNext() )
            String item = (String)iter.next();
            if( item.equalsIgnoreCase( key ) )
                items.remove( index );
                break;
            index ++;
}

Answer 1

That other post looks different, though - the OP is now manipulating the model.The OPs statement of the problem was:
Adding new data to the exitsting model causes the JList to display blank when I refresh the screen.
The suggestion in the other posting was to change the model not the array and the tutorial has a working example of this.
The OPs question was:
When my action performed creates a new instance of the model everything works fine but is this how it should work?
The answer to this is no, you don't need to change the model, just update the model.
So if the OP read the other posting and read the tutorial they should have an answer to their problem.
As you suggested there is no need to create a custom model. The example in the tutorial uses the default list model, if the OP read the tutorial they would know that.