关于在树的节点添加自节点的问题

public TreeNode increasingBST(TreeNode root) {

        ArrayList<Integer> list = new ArrayList<>();

        mid(root,list);

        TreeNode node = new TreeNode();

        TreeNode current = node;

        for(int a : list){

            current = new TreeNode(a);

            current = current.right;

        }

        return node;

    }

public TreeNode increasingBST(TreeNode root) {

        ArrayList<Integer> list = new ArrayList<>();

        mid(root,list);

        TreeNode node = new TreeNode(-1);

        TreeNode current = node;

        for(int a : list){

            current.right = new TreeNode(a);

            current = current.right;

        }

        return node.right;

    }