当节点扩大时，JTree扩大宽度

    fileSystemModel = new MyModel(new File(directory));
    fileTree = new JTree(fileSystemModel);
    fileTree.setEditable(true);
    fileTree.setDragEnabled(true);
    fileTree.addTreeSelectionListener(new TreeSelectionListener() {

        public void valueChanged(TreeSelectionEvent event) {
            File file = (File) fileTree.getLastSelectedPathComponent();
        }
    });

fileTree.setMaximumSize(width, height);

FlowLayout

setVisibleRowCount()

pack()