Preorder Traversal of binary tree in Java

1. Display the data part of the root (or current node).

2. Traverse the left subtree by recursively calling the pre-order function.

3. Traverse the right subtree by recursively calling the pre-order function.

class Node {

     int key;

     Node left, right;

     public Node(int item) {

           key = item;

           left = right = null;

     }

}

class BinaryTree {

     /** Root of Binary Tree*/

     Node root;

     BinaryTree() {

           root = null;

     }

     /** Inorder binary tree traversal. */

     void printPreorder(Node node) {

           if(node==null) {

                return;

           }

           System.out.print(node.key +" ");

          

           printPreorder(node.left);

           printPreorder(node.right);

     }

     /** Call InPrder traversal. */

     void printPreorder() {

           printPreorder(root);

     }

}

public class PreorderTraversal {

     public static void main(String[] args) {

           BinaryTree bTree = new BinaryTree();

           bTree.root = new Node(1);

           bTree.root.left = new Node(2);

           bTree.root.right = new Node(3);

           bTree.root.left.left = new Node(4);

           bTree.root.left.right = new Node(5);

           bTree.root.left.left.left = new Node(6);

           bTree.root.left.left.right = new Node(7);

           System.out.println("Preorder traversal of binary tree is ");

           bTree.printPreorder();

     }

}