如何编写在二叉树(java)中按级别顺序(从左到右)插入节点的方法？

class TreeNode {
    int val;
    TreeNode left;
    TreeNode right;

    public TreeNode(int val) {
        this.val = val;
    }
}

Queue<TreeNode> queue = new LinkedList<>();

if (root == null) {
    root = new TreeNode(val);
    return root;
}

queue.offer(root);

while (!queue.isEmpty()) {
    TreeNode parent = queue.poll();

    // 尝试插入左子节点
    if (parent.left == null) {
        parent.left = new TreeNode(val);
        return root;
    } else {
        queue.offer(parent.left);
    }

    // 尝试插入右子节点
    if (parent.right == null) {
        parent.right = new TreeNode(val);
        return root;
    } else {
        queue.offer(parent.right);
    }
}

class TreeNode {
    int val;
    TreeNode left;
    TreeNode right;

    public TreeNode(int val) {
        this.val = val;
    }
}

public class BinaryTreeInsertion {
    public static TreeNode insertLevelOrder(TreeNode root, int val) {
        Queue<TreeNode> queue = new LinkedList<>();

        if (root == null) {
            root = new TreeNode(val);
            return root;
        }

        queue.offer(root);

        while (!queue.isEmpty()) {
            TreeNode parent = queue.poll();

            // 尝试插入左子节点
            if (parent.left == null) {
                parent.left = new TreeNode(val);
                return root;
            } else {
                queue.offer(parent.left);
            }

            // 尝试插入右子节点
            if (parent.right == null) {
                parent.right = new TreeNode(val);
                return root;
            } else {
                queue.offer(parent.right);
            }
        }

        return root;
    }

    public static void main(String[] args) {
        TreeNode root = null;
        root = insertLevelOrder(root, 1);
        root = insertLevelOrder(root, 2);
        root = insertLevelOrder(root, 3);
        root = insertLevelOrder(root, 4);
        root = insertLevelOrder(root, 5);
    }
}