Check if a given Binary Tree is Heap

CheckMaxHeap.java

// http://www.geeksforgeeks.org/check-if-a-given-binary-tree-is-heap/
// Using level order traversal
import java.util.Stack;
import java.util.Queue;
import java.util.LinkedList;

class Node {
    int data;
    Node left, right;

    public Node(int item) {
        data = item;
        left = null;
        right = null;
    }
}

class BinaryTree {

    Node root;

    boolean checkMaxHeap() 
    {
       Queue<Node> queue = new LinkedList<Node>();
       queue.add(root);
        
       boolean leftNullFound = false;
        
       while(!queue.isEmpty()) {
           
           Node temp = queue.poll();
           
           if (temp.left != null) 
           {
             // if a null left node has been found, then no other left node should exist to satify the complete binary tree property
             if(leftNullFound == true) 
             {
                 return false;    
             }  
             
             if (temp.data > temp.left.data) 
             {
                 queue.add(temp.left);
             }   
             else 
             {
                 return false;
             }
           } 
           else
           {
               leftNullFound = true;
           }
           
           if(temp.right != null) 
           { 
               // if a null left node has been found, then no right node should exist to satify the complete binary tree property
               if(leftNullFound == true) 
               {
                    return false;    
               }
               
               if (temp.data > temp.right.data) 
               {
                 queue.add(temp.right);
               } else{
                   return false;
               }
           }
       }
        return true;
    }
    
   
    
    public static void main(String args[]) 
    {
        BinaryTree tree_level = new BinaryTree();
        tree_level.root = new Node(97);
        tree_level.root.left = new Node(46);
        tree_level.root.right = new Node(37);
        tree_level.root.left.left = new Node(12);
        tree_level.root.left.right = new Node(3);
        
        //tree_level.root.left.right.left = new Node(2);
        //tree_level.root.left.right.right = new Node(1);
            
        tree_level.root.right.left = new Node(7);
        tree_level.root.right.right = new Node(31);
        
        boolean res = tree_level.checkMaxHeap();
        if (res) {
                System.out.println(" Max Heap");
        } else {
                System.out.println(" Not a Max Heap");
        }
    }
}