IntNode class for a tree of integers
``````
public class IntNode {
private int data;
private IntNode left;
private IntNode right;

public IntNode(int data) {
this.data = data;
}

public int getData() {
return data;
}

public IntNode getLeft() {
return left;
}

public void setData(int data) {
this.data = data;
}

public IntNode getRight() {
return right;
}

public void setLeft(IntNode theleft) {
left = theleft;
}

public void setRight(IntNode theright) {
right = theright;
}

// recursive in-order traversal
public void inorder() {
if (left != null) left.inorder();
System.out.println(data);
if (right != null) right.inorder();
}

public int countNodes() {
int leftCount = 0, rightCount = 0;
if (left != null) leftCount = left.countNodes();
if (right != null) rightCount = right.countNodes();
return 1 + leftCount + rightCount;
}
}

``````

The code for binary search tree written in class.
``````
public class IntBST {
private IntNode root;

// constructor
public IntBST() {
// do nothing
}

public boolean isEmpty() {
return (root == null);
}

// returns the address of the IntNode containing n
// if there is no such node, returns null
// Author: Nate Fortuna
public IntNode search (int n) {
IntNode node = root;
while(node != null && node.getData() != n){
if (n > node.getData()){
node = node.getRight();
}else{
node = node.getLeft();
}
}
return node;
}

// inserts n into the Binary Search Tree
// returns the address of the new IntNode containing n
// if there already is such a node, the method doesn't
// create a new node and returns null
// Author: Rob Jansen
public IntNode insert (int n) {
IntNode node = root;

while(true)
{
if(node == null)
{
root = new IntNode(n);
return root;
}
else if(n > node.getData())
{
if(node.getRight() == null)
{
node.setRight(new IntNode(n));
return node.getRight();
}
else
{
node = node.getRight();
}
}
else if(n < node.getData())
{
if(node.getLeft() == null)
{
node.setLeft(new IntNode(n));
return node.getLeft();
}
else
{
node = node.getLeft();
}
}
else
{
return null;
}
}
//return null;
}

public void inorder() {
if (root != null) root.inorder();
}

public int countNodes() {
if (root != null) return root.countNodes();
return 0;
}

}
``````

Testing program:
``````
public class TestIntBST {
public static void main(String [] args) {
IntBST bst = new IntBST();

bst.insert(6);
bst.insert(2);
bst.insert(8);
bst.insert(5);
bst.insert(3);
bst.insert(10);
System.out.println(bst.insert(5));

for (int i = 1; i <= 10; ++i) {
IntNode node = bst.search(i);
if (node != null) {
System.out.println(node.getData());
}
}

bst.inOrder();
System.out.println(bst.countNodes());
}
}
``````

This is an example from CSci 2101 course.

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