// use a layout that will stretch tree to panel size
setLayout(new BorderLayout());
// Create tree
tree = new JTree(tm);
// Change line style
tree.putClientProperty("JTree.lineStyle", "Angled");
// Add TreeSelectionListener
if (listener != null)
tree.addTreeSelectionListener(listener);
// Put tree in a scrollable pane's viewport
JScrollPane sp = new JScrollPane();
sp.getViewport().add(tree);
add(sp, BorderLayout.CENTER);
