Why not used constructor for node class

As far i seen we need constructor for node class but here in binary search tree does not use constructor for node class why?

public class BST {

private class Node {
	int data;
	Node left;
	Node right;
}

private Node root;

public BST(int[] arr) {

	this.root = construct(arr, 0, arr.length - 1);
}

private Node construct(int[] arr, int lo, int hi) {

	if (lo > hi) {
		return null;
	}

	// mid
	int mid = (lo + hi) / 2;

	// create a new node
	Node nn = new Node();
	nn.data = arr[mid];

	nn.left = construct(arr, lo, mid - 1);
	nn.right = construct(arr, mid + 1, hi);

	return nn;
}

hey @Nkc
create a default constructor if you don’t write your own.