BFS Using Adjacency List

// "static void main" must be defined in a public class.
public class Main {
    public static void main(String[] args) {
        int noOfVertices = 8;
        int noOfEdges = 8;
        
        List<Integer>[] adj=new ArrayList[noOfVertices];
        
        List<Integer> list=new ArrayList<>();
        list.add(1);
        adj[0]=list;
        
        list=new ArrayList<>();
        list.add(2);
        list.add(7);
        adj[1]=list;
        
        list=new ArrayList<>();
        list.add(3);
        list.add(4);
        adj[2]=list;
        
        //adj[3]=Arrays.asList(new int[]{});
        
        list=new ArrayList<>();
        list.add(5);
        list.add(6);
        adj[4]=list;
        
        //adj[5]=Arrays.asList(new int[]{});
        //adj[6]=Arrays.asList(new int[]{});
        
        list=new ArrayList<>();
        list.add(4);
        adj[7]=list;
        
        boolean[] visited = new boolean[noOfVertices];
        
        Queue<Integer> q=new LinkedList<>();
        q.add(0);
        
        while(!q.isEmpty()){
            int size=q.size();
            
            Set<Integer> set=new HashSet<>();
            while(size-->0){
                int val=q.remove();
                System.out.println(val+" -> "+(char)('A'+val));
                visited[val]=true;
                
                if(adj[val]!=null){
                    for(int i:adj[val]){
                        if(!visited[i])
                            set.add(i);
                    }
                }
                
            }
            q.addAll(new ArrayList<Integer>(set));
        }
    }    
}