BinarySearchTree.java

public class BinarySearchTreeApp {

    public static void main(String[] args) {

        BSTree t = new BSTree();
        t.addNode(10);
        t.addNode(5);
        t.addNode(3);
        t.addNode(20);
        t.addNode(6);
        t.addNode(15);
        t.addNode(2);
        t.addNode(25);

        System.out.println("----In Order------");
        t.inOrderTraversal(t.root);
        System.out.println("-----Pre Order-----");
        t.preOrderTraversal(t.root);
        System.out.println("----Post Order------");
        t.postOrderTraversal(t.root);

        System.out.println("finding 6 " + t.findNode(6));
        System.out.println("finding 9 " + t.findNode(9));

    }

}

class BSTNode {

    int data;
    BSTNode leftChild;
    BSTNode rightChild;

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

    public String toString() {
        return "data -> " + data;
    }
}

class BSTree {

    BSTNode root;

    public void addNode(int data) {
        BSTNode newNode = new BSTNode(data);
        if (root == null) {
            root = newNode;
        } else {
            BSTNode currentNode = root;
            while (true) {
                BSTNode parentNode = currentNode;
                if (newNode.data < currentNode.data) {
                    currentNode = currentNode.leftChild;
                    if (currentNode == null) {
                        parentNode.leftChild = newNode;
                        return;
                    }
                } else {
                    currentNode = currentNode.rightChild;
                    if (currentNode == null) {
                        parentNode.rightChild = newNode;
                        return;
                    }
                }
            }
        }

    }

    public BSTNode findNode(int data) {
        BSTNode currentNode = root;
        while (currentNode != null) {
            if (data == currentNode.data) {
                return currentNode;

            } else {
                if (data < currentNode.data) {
                    currentNode = currentNode.leftChild;
                } else {
                    currentNode = currentNode.rightChild;
                }
            }
        }
        return null;
    }

    public void preOrderTraversal(BSTNode currentNode) {

        if (currentNode == null) {
            return;
        }

        System.out.println(currentNode);
        preOrderTraversal(currentNode.leftChild);
        preOrderTraversal(currentNode.rightChild);
    }

    public void postOrderTraversal(BSTNode currentNode) {
        if (currentNode == null) {
            return;
        }
        postOrderTraversal(currentNode.leftChild);
        postOrderTraversal(currentNode.rightChild);
        System.out.println(currentNode);
    }

    public void inOrderTraversal(BSTNode currentNode) {
        if (currentNode == null) {
            return;
        }
        inOrderTraversal(currentNode.leftChild);
        System.out.println(currentNode);
        inOrderTraversal(currentNode.rightChild);

    }

}