root.setExpanded (false);
public static void main (String [] args) {	final Display display = new Display ();	final Shell shell = new Shell (display);	shell.setText ("Lazy Tree");	shell.setLayout (new FillLayout ());	final Tree tree = new Tree (shell, SWT.BORDER);	File [] roots = File.listRoots ();	for (int i=0; i<roots.length; i++) {		TreeItem root = new TreeItem (tree, 0);		root.setText (roots [i].toString ());		root.setData (roots [i]);		new TreeItem (root, 0);	}	tree.addListener (SWT.Expand, new Listener () {		public void handleEvent (final Event event) {			final TreeItem root = (TreeItem) event.item;			TreeItem [] items = root.getItems ();			for (int i= 0; i<items.length; i++) {				if (items [i].getData () != null) return;				items [i].dispose ();			}			File file = (File) root.getData ();			File [] files = file.listFiles ();			if (files == null) return;			for (int i= 0; i<files.length; i++) {				TreeItem item = new TreeItem (root, 0);				item.setText (files [i].getName ());				item.setData (files [i]);				if (files [i].isDirectory()) {					new TreeItem (item, 0);					root.setExpanded (false);				}			}		}	});	Point size = tree.computeSize (300, SWT.DEFAULT);	int width = Math.max (300, size.x);	int height = Math.max (300, size.y);	shell.setSize (shell.computeSize (width, height));	shell.open ();	while (!shell.isDisposed ()) {		if (!display.readAndDispatch ()) display.sleep ();	}	display.dispose ();}