isomorphic bt java

// http://code2begin.blogspot.com
// program to check if 2 given binary trees are isomorphic or not

/**
 * Created by MOHIT on 25-05-2018.
 */

import java.util.*;

// node class
class node{
    int data;
    node left;
    node right;

    // function that returns a pointer to new node
    public node(int element){
        this.data = element;
        this.left = null;
        this.right = null;

    }
};

public class BinaryTree {

    // function to check if 2 given trees are isomorphic to each other
    static boolean isomorphic_tree(node root1, node root2){
        // if both the nodes are null then return true
        if (root1 == null && root2 == null){
            return true;
        }
        // if any one of them is null then return false
        if (root1 == null || root2 == null){
            return false;
        }
        // if the data fields are not equal then return false
        if (root1.data != root2.data){
            return false;
        }
        // else check if the left and the right subtrees are isomorphic recursively
        return (
            ( isomorphic_tree(root1.left, root2.left) && isomorphic_tree(root1.right, root2.right) ) ||
            ( isomorphic_tree(root1.left, root2.right) && isomorphic_tree(root1.right, root2.left) )
        );
    }


    public static void main(String arg[]) {
        node head = new node(1);
        head.left = new node(2);
        head.right = new node(3);
        head.left.left = new node(4);
        head.left.right = new node(5);
        head.right.right = new node(6);
        head.left.left.right = new node(7);
        head.right.right.left = new node(8);
        head.left.left.right.left = new node(9);
        head.left.left.right.left.left = new node(10);
        head.right.right.left.right = new node(11);


        node head2 = new node(5);
        head2.left = new node(2);
        head2.right = new node(12);
        head2.left.left = new node(-4);
        head2.left.right = new node(3);
        head2.right.left = new node(9);
        head2.right.right = new node(21);
        head2.right.right.left = new node(19);
        head2.right.right.right = new node(25);


        node i1 = new node(1);
        i1.left = new node(2);
        i1.right = new node(3);
        i1.left.left = new node(4);
        i1.left.right = new node(5);
        i1.right.left = new node(6);
        i1.left.right.left = new node(7);
        i1.left.right.right = new node(8);


        node i2 = new node(1);
        i2.left = new node(3);
        i2.right = new node(2);
        i2.right.left = new node(4);
        i2.right.right = new node(5);
        i2.left.right = new node(6);
        i2.right.right.right = new node(7);
        i2.right.right.left = new node(8);


        System.out.println("TREE #1 and TREE #2 are isomorphic : " + isomorphic_tree(head, head2));
        System.out.println("TREE #3 and TREE #4 are isomorphic : " + isomorphic_tree(i1, i2));

    }
}