Preorder Traversal of Binary tree using stack

PreorderStack.java

import java.util.Stack;

class Node
{
    int data;
    Node left;
    Node right;
    
    public Node(int data){
        this.data = data; 
    }
}

//main class
public class Main {
    
    //Recursive
    public void preorderRecursive(Node root)
    {
        if(root != null){
            System.out.print(root.data + " ");
            preorderRecursive(root.left);
            preorderRecursive(root.right);
            }
    }
    
    //stack 
    public void inorderStack(Node root)
    {
		Stack<Node> s = new Stack<Node>();
		while (true) {
			// First print the root node and then add left node
			while (root != null) {
				System.out.print(root.data + " ");
				s.push(root);
				root = root.left;
			}
			// check if Stack is emtpy, if yes, exit from everywhere
			if (s.isEmpty()) {
				return;
			}
			// pop the element from the stack and go right to the tree
			root = s.pop();
			root = root.right;
		}
    }

    public static void main(String[] args) {
        Node root = new Node(1);
        root.left = new Node(2);
        root.right = new Node(3);
        root.left.left = new Node(4);
		root.left.right = new Node(5);
        root.right.left = new Node(6);
		root.right.right = new Node(7);
		
        
        Main obj = new Main();
        obj.preorderRecursive(root);
        System.out.println();
        obj.inorderStack(root);
    }
}