JTree - Problema com recursividade

import java.awt.event.KeyEvent;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import java.awt.Event;
import java.awt.BorderLayout;
import javax.swing.SwingConstants;
import javax.swing.SwingUtilities;
import javax.swing.KeyStroke;
import java.awt.Point;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JMenuItem;
import javax.swing.JMenuBar;
import javax.swing.JMenu;
import javax.swing.JFrame;
import javax.swing.JDialog;
import java.awt.Dimension;
import javax.swing.JScrollPane;
import java.awt.Rectangle;
import java.io.File;
import java.io.FileFilter;
import java.util.ArrayList;
import java.util.Arrays;

import javax.swing.JTree;
import javax.swing.tree.DefaultMutableTreeNode;

public class tela {

	private JFrame jFrame = null;  //  @jve:decl-index=0:visual-constraint="10,10"
	private JPanel jContentPane = null;
	private JScrollPane jScrollPane = null;
	private JTree jTree = null;
	


	/**
	 * This method initializes jScrollPane	
	 * 	
	 * @return javax.swing.JScrollPane	
	 */
	private JScrollPane getJScrollPane() {
		if (jScrollPane == null) {
			jScrollPane = new JScrollPane();
			jScrollPane.setBounds(new Rectangle(4, 4, 177, 458));
			jScrollPane.setViewportView(getJTree());
		}
		return jScrollPane;
	}

	/**
	 * This method initializes jTree	
	 * 	
	 * @return javax.swing.JTree	
	 */
	private JTree getJTree() {
		if (jTree == null) {
			
			
			File raizes[]= File.listRoots();
			
			DefaultMutableTreeNode raiz = new DefaultMutableTreeNode(raizes[0]);
			
			File nos[] = raizes[0].listFiles();
			Arrays.sort(nos);
			for(int i=0;i<nos.length;i++)
			{
				DefaultMutableTreeNode no= new DefaultMutableTreeNode(nos[i].getName());
				if(nos[i].canRead()){
					if(nos[i].isDirectory())
					{
						no=dir(nos[i]);
						//no= new DefaultMutableTreeNode(nos[i].getName());
	
					}
					
					raiz.add(no);
				}
			 }
			
			
			
			jTree = new JTree(raiz);
		}
		return jTree;
	}
	
	public DefaultMutableTreeNode dir(File arq)
	{
		DefaultMutableTreeNode no = new DefaultMutableTreeNode(arq.getName());
		
		File files[]=arq.listFiles();/*new FileFilter(){
			
			public boolean accept(File dir) {
                return dir.isFile();}
			
		});*/
		
		for(int i=0;i<files.length;i++)
		{	
			if(files[i].canRead())
			{
				//if(files[i].isHidden()){
					if(files[i].isFile()){
					   no.add(new DefaultMutableTreeNode(files[i].getName()));
					}
					else
					{	if(files[i].isDirectory())
						  no.add(dir(files[i]));
					}
				//}
			}
		}
	

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		SwingUtilities.invokeLater(new Runnable() {
			public void run() {
				tela application = new tela();
				application.getJFrame().setVisible(true);
			}
		});
	}

	/**
	 * This method initializes jFrame
	 * 
	 * @return javax.swing.JFrame
	 */
	private JFrame getJFrame() {
		if (jFrame == null) {
			jFrame = new JFrame();
			jFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
			jFrame.setSize(617, 495);
			jFrame.setContentPane(getJContentPane());
			jFrame.setTitle("Application");
		}
		return jFrame;
	}

	/**
	 * This method initializes jContentPane
	 * 
	 * @return javax.swing.JPanel
	 */
	private JPanel getJContentPane() {
		if (jContentPane == null) {
			jContentPane = new JPanel();
			jContentPane.setLayout(null);
			jContentPane.add(getJScrollPane(), null);
			
		}
		return jContentPane;
	}

}