How do you create tree data structure ?

1. /* Class containing left and right child of current
2. node and data value*/
3. class Node
4. {
5. int data;
6. Node left, right;
7. 
   
8. public Node(int data1)
9. {
10. data = data1;
11. left = right = null;
12. }
13. }
14. 
    
15. // A Java program to introduce Binary Tree
16. class BinaryTree
17. {
18. // Root of Binary Tree
19. Node root;
20. 
    
21. // Constructors
22. BinaryTree(int data1)
23. {
24. root = new Node(data1);
25. }
26. 
    
27. BinaryTree()
28. {
29. root = null;
30. }
31. 
    
32. public static void main(String[] args)
33. {
34. BinaryTree tree = new BinaryTree();
35. 
    
36. /*create root*/
37. tree.root = new Node(1);
38. 
    
39. /* following is the tree after above statement
40.  
41.               1
42.             /   \
43.           null  null     */
44. 
    
45. tree.root.left = new Node(2);
46. tree.root.right = new Node(3);
47. 
    
48. /* 2 and 3 become left and right children of 1
49.                1
50.              /   \
51.             2      3
52.           /    \    /  \
53.         null null null null  */
54. 
    
55. 
    
56. tree.root.left.left = new Node(4);
57. tree.root.left.left.right = new Node(9);
58.         /* 4 becomes left child of 2
59.                     1
60.                 /       \
61.                2          3
62.              /   \       /  \
63.             4    null  null  null
64.            /   \
65.           null 9
66.          */
67. System.out.println(tree.root.right.data);
68. }
69. }

Output: 3