Binary Tree Traversal - InOrder, PreOrder, PostOrder - Depth First Traversal

BTTraversal.java

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;
    }

    public static void main(String[] args)
    {
        BinaryTree tree = new BinaryTree();

        tree.root = new Node(1);
        Node second  = new Node(2);
        second.left  = new Node(4);
        second.right = new Node(5);
        tree.root.left = second;
        tree.root.right = new Node(3);
        
        System.out.println(" Inorder ");
        tree.printInorder();
        System.out.println(" Preorder ");
        tree.printPreorder();
        System.out.println(" Postorder ");
        tree.printPostorder();
    }
    
     public void printPostorder()
    {
        postorder(root);    
    }
    
    public void postorder(Node root) 
    {
        // Left, Right, Root
        if(root == null) {
            return;
        }
        
        postorder(root.left);
        postorder(root.right);
        System.out.print(root.key + " ");
    }
    
    public void printPreorder()
    {
        preorder(root);    
    }
    
    public void preorder(Node root) 
    {
        // Root Left Right
        if(root == null) {
            return;
        }
        
        System.out.print(root.key + " ");
        preorder(root.left);
        preorder(root.right);
    }
    
    public void printInorder()
    {
        inorder(root);    
    }
    
    public void inorder(Node root) 
    {
        // Left Root Right
        if(root == null) {
            return;
        }
        
        inorder(root.left);
        System.out.print(root.key + " ");
        inorder(root.right);
    }
}