Java Program to check the given Binary Tree is Binary Search Tree(BST) or not ?

package com.practice;

classNode{

int data;
      Node leftChild;
      Node rightChild;

publicNode(int data){
this.data= data;
           leftChild =null;
           rightChild =null;
}
}

publicclassBSTValidation{
      Node root;
publicbooleanisBinarySearchTree(){

if(root ==null)return Boolean.TRUE;
returnisBstValid(root, Integer.MIN_VALUE, Integer.MAX_VALUE);
}

privatebooleanisBstValid(Node node, Integer minValue, Integer maxValue){

if(node ==null)return Boolean.TRUE;
if(node.data>= minValue && node.data< maxValue
&& isBstValid(node.leftChild, minValue, node.data)
&& isBstValid(node.rightChild, node.data, maxValue)){
return Boolean.TRUE;
}else{
return Boolean.FALSE;
}
}

publicstaticvoidmain(String[] args){

             BSTValidation tree =new BSTValidation();

             // first example, valid binary search tree
             tree.root=new Node(48);
             tree.root.leftChild=new Node(22);
             tree.root.rightChild=new Node(61);
             tree.root.leftChild.leftChild=new Node(12);
             tree.root.leftChild.rightChild=new Node(28);
             tree.root.rightChild.leftChild=new Node(54);
             tree.root.rightChild.rightChild=new Node(68);
             System.out.println(tree.isBinarySearchTree());

// second example, not a valid bst

             tree.root=new Node(48);
             tree.root.leftChild=new Node(22);
             tree.root.rightChild=new Node(100);
             tree.root.leftChild.leftChild=new Node(12);
             tree.root.leftChild.rightChild=new Node(28);
             tree.root.rightChild.leftChild=new Node(54);
             tree.root.rightChild.rightChild=new Node(68);
             System.out.println(tree.isBinarySearchTree());
}
}