JavaBinarySearchTreeTraversals

//define node of the BST
class Node {
    int key;
    Node left, right;

    public Node(int data){
        key = data;
        left = right = null;
    }
}
//BST class
class BST_class {
    // BST root node
    Node root;

    BST_class(){
        root = null;
    }

    //PostOrder Traversal - Left:Right:rootNode (LRn)
    void postOrder(Node node)  {
        if (node == null)
            return;

        // first traverse left subtree recursively
        postOrder(node.left);

        // then traverse right subtree recursively
        postOrder(node.right);

        // now process root node
        System.out.print(node.key + " ");
    }
    // InOrder Traversal - Left:rootNode:Right (LnR)
    void inOrder(Node node)  {
        if (node == null)
            return;
        //first traverse left subtree recursively
        inOrder(node.left);

        //then go for root node
        System.out.print(node.key + " ");

        //next traverse right subtree recursively
        inOrder(node.right);
    }

    //PreOrder Traversal - rootNode:Left:Right (nLR)
    void preOrder(Node node)  {
        if (node == null)
            return;

        //first print root node first
        System.out.print(node.key + " ");
        // then traverse left subtree recursively
        preOrder(node.left);
        // next traverse right subtree recursively
        preOrder(node.right);
    }
    // Wrappers for recursive functions
    void postOrder_traversal()  {
        postOrder(root);  }
    void inOrder_traversal() {
        inOrder(root);   }
    void preOrder_traversal() {
        preOrder(root);  }
}
class Main{
    public static void main(String[] args) {
        //construct a BST
        BST_class tree = new BST_class();
        /*        45
                //  \\
                10   90
               // \\
               7   12      */
        tree.root = new Node(45);
        tree.root.left = new Node(10);
        tree.root.right = new Node(90);
        tree.root.left.left = new Node(7);
        tree.root.left.right = new Node(12);
        //PreOrder Traversal
        System.out.println("BST => PreOrder Traversal:");
        tree.preOrder_traversal();
        //InOrder Traversal
        System.out.println("\nBST => InOrder Traversal:");
        tree.inOrder_traversal();
        //PostOrder Traversal
        System.out.println("\nBST => PostOrder Traversal:");
        tree.postOrder_traversal();
    }
}