Print Top View of Binary Tree

package org.wesome.dsalgo;

import lombok.Data;

import java.util.LinkedList;
import java.util.Map;
import java.util.Objects;
import java.util.Queue;
import java.util.TreeMap;

public class BinarySearchTree {
    Node root;

    void insert(int data) {
        System.out.println("BinarySearchTree.insert data = " + data);
        root = insert(root, data);
    }

    Node insert(Node root, int data) {
        if (Objects.isNull(root)) {
            Node tempNode = new Node(data);
            return tempNode;
        }
        if (data > root.data) {
            root.right = insert(root.right, data);
        } else {
            root.left = insert(root.left, data);
        }
        return root;
    }

    public static void topView(Node root) {
        if (Objects.isNull(root)) {
            return;
        }
        int hrzDis = 0;
        TreeMap<Integer, Integer> map = new TreeMap<>();
        // create a queue for level order traversal
        Queue<Node> queue = new LinkedList<>();
        // Assign initialized horizontal distance value to root node and add it to the queue.
        root.hrzDis = hrzDis;
        // add root with level 0
        queue.add(root);
        while (!queue.isEmpty()) {
            Node tnode = queue.poll();
            hrzDis = tnode.hrzDis;
            // check if this is the first node for this level
            if (!map.containsKey(hrzDis)) {
                map.put(hrzDis, tnode.data);
            }
            // add left child in the queue with horizontal distance hrzDis-1.
            if (Objects.nonNull(tnode.left)) {
                tnode.left.hrzDis = hrzDis - 1;
                queue.add(tnode.left);
            }
            // add right child in the queue with horizontal distance hrzDis+1.
            if (Objects.nonNull(tnode.right)) {
                tnode.right.hrzDis = hrzDis + 1;
                queue.add(tnode.right);
            }
        }
        for (Map.Entry<Integer, Integer> entry : map.entrySet()) {
            System.out.print(entry.getValue() + " ");
        }
    }
}

@Data
class Node {
    int data;
    Node left;
    Node right;
    int hrzDis;

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

package org.wesome.dsalgo;

import org.junit.jupiter.api.Test;

public class BinarySearchTreeTest {
    @Test
    void topViewTest() {
        BinarySearchTree binarySearchTree = new BinarySearchTree();
        binarySearchTree.insert(4);
        binarySearchTree.insert(2);
        binarySearchTree.insert(1);
        binarySearchTree.insert(3);
        binarySearchTree.insert(6);
        binarySearchTree.insert(5);
        binarySearchTree.insert(7);
        binarySearchTree.topView(binarySearchTree.root);
    }
}

plugins {
    id 'java'
    id "io.freefair.lombok" version "6.2.0"
}

group = 'org.wesome'
version = '0.0.1-SNAPSHOT'
sourceCompatibility = JavaVersion.VERSION_1_8

configurations {
    compileOnly {
        extendsFrom annotationProcessor
    }
}

repositories {
    mavenCentral()
}

dependencies {
    testImplementation 'org.junit.jupiter:junit-jupiter:5.6.2'
}

test {
    useJUnitPlatform()
}