import java.io.*;
import java.util.ArrayList;

import javax.swing.*;

public class BadLazyListModelExample {

  static class BadLazyListModel extends AbstractListModel {

    public int getSize() {
      return list.size();
    }

    public Object getElementAt(int index) {
      return list.get(index);
    }

    public void safeAdd(final File file) {
      SwingUtilities.invokeLater(new Runnable() {
        public void run() {
          int index= list.size();
          list.add(file);
          fireIntervalAdded(BadLazyListModel.this, index, index);
        }
      });
    }

    public void traverse(File file) {
      File[] files= file.listFiles(filter);
      for (int i= 0; i < files.length; i++) {
        safeAdd(files[i]);
        traverse(files[i]);
      }
    }

    final ArrayList list= new ArrayList();
    private final FileFilter filter=new FileFilter() {
      public boolean accept(File file) {
        return file.isDirectory();
      }
    };
  }

  public static void main(String[] args) {

    BadLazyListModel model= new BadLazyListModel();
    JList list= new JList(model);
    JScrollPane pane= new JScrollPane(list);

    final JFrame frame= new JFrame();
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setContentPane(pane);
    frame.setSize(400, 300);
    frame.show();

    File dir;
    if (args.length > 0)
      dir= new File(args[0]);
    else
      dir= new File(".");

    model.traverse(dir);
  }
}