Check if a binary tree is a mirror image or symmetric

How about calling mirrorEquals(root.left, root.right) on the following function :-

boolean mirrorEquals(BTree left, BTree right) {
  if (left == null || right == null) return left == null && right == null;
  return left.value == right.value
     && mirrorEquals(left.left, right.right)
     && mirrorEquals(left.right, right.left);
}

Basically compare the left subtree and inverted right subtree, drawing an imaginary line of inversion across root.