jtree 默认展开树的全部节点

    public static void expandTree(JTree tree) { 
        TreeNode root = (TreeNode) tree.getModel().getRoot(); 
        expandAll(tree, new TreePath(root), true); 
    } 

   
    private static void expandAll(JTree tree, TreePath parent, boolean expand) { 
        // Traverse children 
        TreeNode node = (TreeNode) parent.getLastPathComponent(); 
        if (node.getChildCount() >= 0) { 
            for (Enumeration e = node.children(); e.hasMoreElements(); ) { 
                TreeNode n = (TreeNode) e.nextElement(); 
                TreePath path = parent.pathByAddingChild(n); 
                expandAll(tree, path, expand); 
            } 
        } 

        // Expansion or collapse must be done bottom-up 
        if (expand) { 
            tree.expandPath(parent); 
        } else { 
            tree.collapsePath(parent); 
        } 
    }