Insertion in Red-Black Tree

/*package whatever //do not write package name here */

import java.io.*;

// considering that you know what are red-black trees here is the implementation in java for insertion and traversal.
// RedBlackTree class. This class contains subclass for node
// as well as all the functionalities of RedBlackTree such as - rotations, insertion and 
// inoredr traversal
public class RedBlackTree
{
    public Node root;//root node
    public RedBlackTree() 
    {
        super();
        root = null;
    }
    // node creating subclass
    class Node
    {
        int data;
        Node left;
        Node right;
        char colour;
        Node parent;

        Node(int data)
        {
            super();
            this.data = data;   // only including data. not key
            this.left = null; // left subtree
            this.right = null; // right subtree
            this.colour = 'R'; // colour . either 'R' or 'B'
            this.parent = null; // required at time of rechecking.
        }
    }
    // this function performs left rotation
    Node rotateLeft(Node node)
    {
        Node x = node.right;
        Node y = x.left;
        x.left = node;
        node.right = y;
        node.parent = x; // parent resetting is also important.
        if(y!=null)
            y.parent = node;
        return(x);
    }
    //this function performs right rotation
    Node rotateRight(Node node)
    {
        Node x = node.left;
        Node y = x.right;
        x.right = node;
        node.left = y;
        node.parent = x;
        if(y!=null)
            y.parent = node;
        return(x);
    }


    // these are some flags.
    // Respective rotations are performed during traceback.
    // rotations are done if flags are true.
    boolean ll = false;
    boolean rr = false;
    boolean lr = false;
    boolean rl = false;
    // helper function for insertion. Actually this function performs all tasks in single pass only.
    Node insertHelp(Node root, int data)
    {
        // f is true when RED RED conflict is there.
        boolean f=false;
        
        //recursive calls to insert at proper position according to BST properties.
        if(root==null)
            return(new Node(data));
        else if(data<root.data)
        {
            root.left = insertHelp(root.left, data);
            root.left.parent = root;
            if(root!=this.root)
            {
                if(root.colour=='R' && root.left.colour=='R')
                    f = true;
            }
        }
        else
        {
            root.right = insertHelp(root.right,data);
            root.right.parent = root;
            if(root!=this.root)
            {
                if(root.colour=='R' && root.right.colour=='R')
                    f = true;
            }
        // at the same time of insertion, we are also assigning parent nodes 
        // also we are checking for RED RED conflicts
        }

        // now lets rotate.
        if(this.ll) // for left rotate.
        {
            root = rotateLeft(root);
            root.colour = 'B';
            root.left.colour = 'R';
            this.ll = false;
        }
        else if(this.rr) // for right rotate
        {
            root = rotateRight(root);
            root.colour = 'B';
            root.right.colour = 'R';
            this.rr  = false;
        }
        else if(this.rl)  // for right and then left
        {
            root.right = rotateRight(root.right);
            root.right.parent = root;
            root = rotateLeft(root);
            root.colour = 'B';
            root.left.colour = 'R';

            this.rl = false;
        }
        else if(this.lr)  // for left and then right.
        {
            root.left = rotateLeft(root.left);
            root.left.parent = root;
            root = rotateRight(root);
            root.colour = 'B';
            root.right.colour = 'R';
            this.lr = false;
        }
        // when rotation and recolouring is done flags are reset.
        // Now lets take care of RED RED conflict
        if(f)
        {
            if(root.parent.right == root)  // to check which child is the current node of its parent
            {
                if(root.parent.left==null || root.parent.left.colour=='B')  // case when parent's sibling is black
                {// perform certaing rotation and recolouring. This will be done while backtracking. Hence setting up respective flags.
                    if(root.left!=null && root.left.colour=='R')
                        this.rl = true;
                    else if(root.right!=null && root.right.colour=='R')
                        this.ll = true;
                }
                else // case when parent's sibling is red
                {
                    root.parent.left.colour = 'B';
                    root.colour = 'B';
                    if(root.parent!=this.root)
                        root.parent.colour = 'R';
                }
            }
            else   
            {
                if(root.parent.right==null || root.parent.right.colour=='B')
                {
                    if(root.left!=null && root.left.colour=='R')
                        this.rr = true;
                    else if(root.right!=null && root.right.colour=='R')
                        this.lr = true;
                }
                else
                {
                    root.parent.right.colour = 'B';
                    root.colour = 'B';
                    if(root.parent!=this.root)
                        root.parent.colour = 'R';
                }
            }
            f = false;
        }
        return(root);  
    }

    // function to insert data into tree.
    public void insert(int data)
    {
        if(this.root==null)
        {
            this.root = new Node(data);
            this.root.colour = 'B';
        }
        else
            this.root = insertHelp(this.root,data);
    }
    // helper function to print inorder traversal
    void inorderTraversalHelper(Node node)
    {
        if(node!=null)
        {
            inorderTraversalHelper(node.left);
            System.out.printf("%d ", node.data);
            inorderTraversalHelper(node.right);
        }
    }
    //function to print inorder traversal
    public void inorderTraversal()
    {
        inorderTraversalHelper(this.root);
    }
    // helper function to print the tree.
    void printTreeHelper(Node root, int space)
    {
        int i;
        if(root != null)
        {
            space = space + 10;
            printTreeHelper(root.right, space); 
            System.out.printf("\n"); 
            for ( i = 10; i < space; i++) 
            {
                System.out.printf(" ");
            } 
            System.out.printf("%d", root.data);
            System.out.printf("\n");
            printTreeHelper(root.left, space); 
        }
    }
    // function to print the tree.
    public void printTree()
    {
        printTreeHelper(this.root, 0);
    }
    public static void main(String[] args) 
    {
        // let us try to insert some data into tree and try to visualize the tree as well as traverse.
        RedBlackTree t = new RedBlackTree();
        int[] arr = {1,4,6,3,5,7,8,2,9};
        for(int i=0;i<9;i++)
        {
            t.insert(arr[i]);
            System.out.println();
            t.inorderTraversal();
        }
        // you can check colour of any node by with its attribute node.colour
        t.printTree();
    }
}