Who says java does not supports pointers part-six, lets implement a Tree in Java, a code by Pankaj

This extraordinary code of Binary Tree is
implemented and provided by
Pankaj, from Nit-Arunachal Pradesh




Note: Binary tree is a non linear data
structure. It is very important and useful
in computer science.
In a binary tree huge amount of data can be
stored and retrieved in a very less period of 
time. So, its time complexity is very good.
For further information on binary tree please
click on given link more about binary tree   




note : before using this code please create a "java project"
in "eclipse" and store all the classes in separate program
files inside "src" folder of "java project".



## save this class inside BTNode.java file ##
import java.util.Scanner;
public class BTNode {

 BTNode left, right;
 int data;

 // Constructor to craete a node
 public BTNode() {
  left = null;
  right = null;
  data = 0;
 }

 // Constructor to put value of data
 public BTNode(int n) {
  left = null;
  right = null;
  data = n;
 }

 // method to join left node
 public void setLeft(BTNode n) {
  left = n;
 }

 // method to join right node
 public void setRight(BTNode n) {
  right = n;
 }

 // method to get left node
 public BTNode getLeft() {
  return left;
 }

 // method to get right node
 public BTNode getRight() {
  return right;
 }

 // method for set data to node
 public void setData(int d) {
  data = d;
 }

 // method to get data from node
 public int getData() {
  return data;
 }
}



## save this class inside BT.java file ##
// Class BT
public class BT {
 private BTNode root;

 public BT() {
  root = null;
 }

 // empty check
 public boolean isEmpty() {
  return root == null;
 }

 public void insert(int data) {
  root = insert(root, data);
 }

 private BTNode insert(BTNode node, int data) {
  if (node == null)
   node = new BTNode(data);
  else {
  if (node.getRight() == null)
   node.right = insert(node.right, data);
   else
  node.left = insert(node.left, data);
  }
  return node;
 }

 // count number of nodes
 public int countNodes() {
  return countNodes(root);
 }

 // count nodes implementation
 private int countNodes(BTNode r) {
  if (r == null)
   return 0;
  else {
   int l = 1;
   l += countNodes(r.getLeft());
   l += countNodes(r.getRight());
   return l;
  }
 }

 // search for an element
 public boolean search(int val) {
  return search(root, val);
 }

 // search implementation
 private boolean search(BTNode r, int val) {
  if (r.getData() == val)
   return true;
  if (r.getLeft() != null)
   if (search(r.getLeft(), val))
    return true;
  if (r.getRight() != null)
   if (search(r.getRight(), val))
    return true;
  return false;
 }

 // inorder traversal
 public void inorder() {
  inorder(root);
 }

 private void inorder(BTNode r) {
  if (r != null) {
   inorder(r.getLeft());
 System.out.print(r.getData() + " ");
   inorder(r.getRight());
  }
 }

 // preorder traversal
 public void preorder() {
  preorder(root);
 }

 private void preorder(BTNode r) {
  if (r != null) {
  System.out.print(r.getData() + " ");
  preorder(r.getLeft());
  preorder(r.getRight());
  }
 }

 // postorder traversal
 public void postorder() {
  postorder(root);
 }

 private void postorder(BTNode r) {
  if (r != null) {
    postorder(r.getLeft());
    postorder(r.getRight());
    System.out.print(r.getData() + " ");
  }
 }
}

## save this class inside BinaryTree.java file ##
public class BinaryTree {
 public static void main(String[] args) {
  Scanner scan = new Scanner(System.in);
  BT bt = new BT();
  System.out.println("Binary Tree Test\n");
  char ch;
  do {
  System.out.println("\nBinary Tree Operations\n");
  System.out.println("press 1 to insert ");
  System.out.println("press 2 to search");
  System.out.println("press 3 to count nodes");
  System.out.println("press 4 to check empty");
  int choice = scan.nextInt();
  switch (choice) {
  case 1:
  System.out.println("Enter integer element to insert");
  bt.insert(scan.nextInt());
  break;
  case 2:
  System.out.println("Enter integer element to search");
        int element = scan.nextInt();
  System.out.println("Search result : " + bt.search(element));
  break;
  case 3:
  System.out.println("Nodes = " + bt.countNodes());
  break;
  case 4:
  System.out.println("Empty status = " + bt.isEmpty());
  break;
  default:
  System.out.println("Wrong Entry \n ");
  break;
  }
  // display the tree
  System.out.print("\nPost order : ");
  bt.postorder();
  System.out.print("\nPre order : ");
  bt.preorder();
  System.out.print("\nIn order : ");
  bt.inorder();
  System.out.println("\n\nDo you want to continue (Type y or n) \n");
  ch = scan.next().charAt(0);
  } while (ch == 'Y' || ch == 'y');
 }
}