ツリーでファイルをリストする

import java.io.File;
import javax.swing.JFrame;
import javax.swing.JTree;
import javax.swing.tree.DefaultMutableTreeNode;

public class ListFileTest {
	public DefaultMutableTreeNode root;
	public ListFileTest() {
		root=new DefaultMutableTreeNode("root");
	}
	public DefaultMutableTreeNode lstFiles(File f,DefaultMutableTreeNode node) {
		if (node == null) {
			node = root;
			lstFiles(f,node);
		} else {
			if (f.isDirectory()) {
				String name=f.getName();
				DefaultMutableTreeNode currentNode = new DefaultMutableTreeNode(name);
				node.add(currentNode);
				File[] files = f.listFiles();
				if (files!=null) {
					for (int i = 0; i < files.length; i++) {
						lstFiles(files[i],currentNode);
					}
				}
			} else {
				DefaultMutableTreeNode currentNode = new DefaultMutableTreeNode(f
						.getName());
				node.add(currentNode);
			}
		}
		return root;
	}

	public static void main(String[] args) {
		File file = new File("F:\\");
		ListFileTest t=new ListFileTest();
		JFrame frame = new JFrame();

frame.addWindowListener(new WindowAdapter() {
			public void windowClosing(WindowEvent e) {
				super.windowClosing(e);
				System.exit(0);
			}
		});

 DefaultMutableTreeNode nodes = t.lstFiles(file,null);

		JTree tree = new JTree(nodes);
		tree.setVisible(true);
		frame.add(tree);
		frame.setTitle("test");
		frame.setSize(300, 400);
		frame.setVisible(true);

	}
}