剑指offer 28 判断二叉树是否对称 Java

如题：

public class BinaryTreeIsSymmertrical28 {
    static class Node {
        int val;
        Node left;
        Node right;
        public Node(int val){
            this.val = val;
        }
        @Override
        public String toString() {
            return "Node{" +
                    "val=" + val +
                    ", left=" + left +
                    ", right=" + right +
                    '}';
        }
    }

    public static void main(String[] args) {
        Node root = new Node(8);
        Node node21 = new Node(6);
        Node node22 = new Node(6);
        Node node31 = new Node(5);
        Node node32 = new Node(7);
        Node node33 = new Node(7);
        Node node34 = new Node(5);
        root.left = node21;
        root.right = node22;
        node21.left = node31;
        node21.right = node32;
        node22.left = node33;
        node22.right = node34;
        System.out.println(isSymmertrical(root, root));
    }

    private static boolean isSymmertrical(Node root1, Node root2) {
        if (root1 == null && root2 == null)
            return true;
        if (root1 == null || root2 == null)
            return false;
        if (root1.val != root2.val)
            return false;
        return isSymmertrical(root1.left, root2.right) && isSymmertrical(root1.right, root2.left);
    }
}