3 different way Tree Traversal

=========================================================================
Node class for tree

class Node{
    int data;
    Node left;
    Node right;
}

=========================================================================
Case 1: pre-order 

Recursive

public static void preOrderRecursive(Node root){
    if(root == null)
        return;
		
    System.out.print(root.data + " ");		
    preOrderRecursive(root.left);
    preOrderRecursive(root.right);
}

NON-Recursive

public static void preOrderIterative(Node root){
    if(root == null)
        return;
		
    Stack<Node> unvisited = new Stack<Node>();
    unvisited.push(root);
	
    while(!unvisited.isEmpty()){
        Node node = unvisited.pop();
			
        System.out.print(node.data + " ");
        if(node.right != null)
            unvisited.push(node.right);
        if(node.left != null)
            unvisited.push(node.left);
    }	
}

=========================================================================
Case 2: in-order 

Recursive

public static void inOrderRecursive(Node root){
    if(root == null)
        return;	
	
    inOrderRecursive(root.left);
    System.out.print(root.data + " ");
    inOrderRecursive(root.right);
}

NON-Recursive

public static void inOrderIterative(Node root){
    if(root == null)
        return;
		
    Stack<Node> unvisited = new Stack<Node>();
		
    while(!unvisited.isEmpty() || root != null){
        if(root != null){
            unvisited.push(root);
            root = root.left;
        }else{
            root = unvisited.pop();
            System.out.print(root.data + " ");
            root = root.right;
        }
    }
}

========================================================================= 
Case 3: post-order 

Recursive

public static void postOrderRecursive(Node root){
    if(root == null)
        return;
		
    postOrderRecursive(root.left);
    postOrderRecursive(root.right);
    System.out.print(root.data + " ");		
}

NON-Recursive

public static void postOrderIterative(Node root){
    if(root == null)
        return;
		
    Stack<Node> finalStack = new Stack<Node>();
    Stack<Node> tempStack = new Stack<Node>();
	
    tempStack.push(root);
    while(!tempStack.isEmpty()){
        Node node = tempStack.pop();
        finalStack.push(node);
        if(node.left != null)
            tempStack.push(node.left);
				
        if(node.right != null)
            tempStack.push(node.right);
    }
	
    while(!finalStack.isEmpty()){
        Node node = finalStack.pop();
        System.out.print(node.data + " ");	
    }
}