BFS traversal of graph represented by adjacency list

import java.util.*;

public class Main

{

    public static void main(String[] args) {

        System.out.println("Hello World");

        HashMap<Integer, ArrayList<Integer>> adjList = new HashMap<>();

        // Adding nodes to the graph

        for (int i = 0; i <= 9; i++) {

            adjList.put(i, new ArrayList<>());

        }

        // Adding edges to the graph

        addEdge(adjList, 0, 1);

        addEdge(adjList, 1, 2);

        addEdge(adjList, 1, 6);

        addEdge(adjList, 2, 3);

        addEdge(adjList, 2, 4);

        addEdge(adjList, 6, 7);

        addEdge(adjList, 4, 5);

        addEdge(adjList, 6, 9);

        addEdge(adjList, 7, 8);

        // Print the adjacency list

        System.out.println("Adjacency List: " + adjList);

        System.out.println("The bfs traversal is:");

        ArrayList < Integer > ans = bfsOfGraph(9, adjList);

        int n = ans.size();

        for(int i = 0;i<n;i++) {

            System.out.print(ans.get(i)+" ");

        }

    }

    public static ArrayList<Integer> bfsOfGraph(int V, HashMap<Integer, ArrayList<Integer>> adjList) { // V is last number(max num) of graph

        ArrayList < Integer > bfs = new ArrayList < > ();

        boolean vis[] = new boolean[V+1];

        Queue < Integer > q = new LinkedList < > ();

        q.add(0);

        vis[0] = true;

        while (!q.isEmpty()) {

            int node = q.poll();

            bfs.add(node);

            for (int it: adjList.get(node)) {

                if (vis[it] == false) {

                    vis[it] = true;

                    q.add(it);

                }

            }

        }

        return bfs;

    }

   

   

    // Helper method to add an edge to the graph

    public static void addEdge(HashMap<Integer, ArrayList<Integer>> adjList, int source, int destination) {

        adjList.get(source).add(destination);

        adjList.get(destination).add(source); // If the graph is undirected

    }

}