root always still null on my binary tree - search

Question

import java.io.*;
class treeNode {
int data;
treeNode left = null;
treeNode right = null;
treeNode parent = null;
treeNode (int value)
{
data = value;
}
}
class treeNodes {
treeNode root = null;
void insert (treeNode node)
{
if (root == null) // the value of root is always null
{
root = node;
return;
}
treeNode cur = null;
treeNode father = null;
while (cur != null)
{
father = cur;
if (cur.data > node.data)
cur = cur.left;
else
cur = cur.right;
}
if (father.data > node.data)
father.left = node;
else
father.right = node;
node.parent = father;
}
void walkInorder (treeNode n)
{
if (n == null)
return;
walkInorder (n.left);
System.out.print (n.data + " ");
walkInorder (n.right);
}
}
class binarySearchTree {
public static void main (String [] args) {
treeNodes obj1 = new treeNodes ( );
System.out.println ("============ Array Elements ============");
int A[] = {3, 5, 7, 9, 8, 6};
for (int i = 0; i < 6; i++)
{
treeNode node = new treeNode (A[i]);
treeNodes obj = new treeNodes ( );
obj.insert(node);
}
System.out.println ("\n============ Inorder ============");
System.out.println (obj1.root.data);
obj1.walkInorder (obj1.root);
}
}
i'm tried to make binary tree and when i send the first value to insert function it should change the value of root
In my case the root never change can someone tell me why and how can i solve it
sorry for my bad english

Answer 1

Inside your for loop, for each item in your array, you are creating a new treeNodes instance. Whenever you create a new instance, root is set to null.
Try making the following change to your for loop:
treeNodes obj = new treeNodes();
for (int i = 0; i < 6; i++)
{
treeNode node = new treeNode(A[i]);
obj.insert(node);
}
This way, every step of your loop will use the same treeNodes instance, and the root node will correctly be set. There are other problems with your code, but part of learning is experimenting. So, go ahead, fix the issue above and let us know how it goes.

Answer 2

I guess the answer above is not completely right. Yes, you'll be creating a new treeNodes instance everytime the loop goes to the next element in your array, but that would mean you were creating new trees with only one element, so the root would not be null.
The roots you are trying to print, in the other hand, are null in fact, but thats because you did not insert any element in the tree you are trying to print.
You tried to walk in order the tree OBJ1, and you didnt insert anything into this tree. You should try to walk in order the tree OBJ.
The answer above is right, you need to make that fix, so you will insert the array elements into only one tree, and then fix this issue i explained.