Is Binary Search Tree - Java

public class IsBST {

public static boolean isBST(Tree treeNode) {
return isBST(treeNode,Integer.MIN_VALUE,Integer.MAX_VALUE);
}

private static boolean isBST(Tree treeNode, int minValue, int maxValue) {
if(treeNode == null)
return true;

if(treeNode.data < minValue || treeNode.data > maxValue)
return false;

if(!isBST(treeNode.left,minValue,treeNode.data) && !isBST(treeNode.right,treeNode.data,maxValue))
return false;

return true;
}

public static void main(String[] args) {
Tree myTree = new Tree(4);
myTree.left = new Tree(2);
myTree.right = new Tree(6);
myTree.left.left = new Tree(1);
myTree.left.right = new Tree(3);
myTree.right.left = new Tree(7);

System.out.println(Boolean.toString(isBST(myTree)));
}

}

class Tree{
int data;
Tree left;
Tree right;
public Tree(int data) {
this.data = data;
this.left = this.right = null;
}
}