Graph

import java.util.ArrayList;
import java.util.HashMap;

class Graph
{
    HashMap<String, ArrayList<String>> adjList = new HashMap<>();
    
    public void printGraph()
    {
        System.out.println(adjList);
    }
    public boolean addVertex(String vertex)
    {
        if(adjList.get(vertex)==null)
        {
            adjList.put(vertex,new ArrayList<String>());
            return true;
        }
        return false;
    }
    public boolean addEdge(String vertex1, String vertex2)
    {
        if(adjList.get(vertex1)!=null && adjList.get(vertex2)!=null)
        {
            adjList.get(vertex1).add(vertex2);
            adjList.get(vertex2).add(vertex1);
            return true;
        }
        return false;
    }
    public boolean removeEdge(String vertex1, String vertex2)
    {
        if(adjList.get(vertex1)!=null && adjList.get(vertex2)!=null)
        {
            adjList.get(vertex1).remove(vertex2);
            adjList.get(vertex2).remove(vertex1);
            return true;
        }
        return false;
    }
}

class Main {
    public static void main(String[] args) {
        Graph myGraph = new Graph();
        myGraph.addVertex("A");
        myGraph.addVertex("B");
        myGraph.addEdge("A","B");
        myGraph.removeEdge("A","B");
        myGraph.printGraph();
    }
}