Reimplement the addNode method of the Node class in BinarySearchTree as a static method of the BinarySearchTree class:

private static Node addNode(Node parent, Node newNode)

If parent is null, return newNode. Otherwise, recursively add newNode to parent and return parent.

Your implementation should replace the three null checks in the add and original addNode methods with just one null check.

Draft: Insert a single node into an empty tree