Write a method that checks if a binary tree is strict

public Boolean isStrictTree(TreeNode node) {
if (node == null) {
    return true;
}
if ((node.left() == null && node.right() != null) || (node.left() != null && node.right() == null)) {
    return false;
}
return isStrictTree(node.left()) && isStrictTree(node.right());
}