Using java please try to complete the TODO part in the 2 methods given below with what is given

This is the graph class

import java.util.ArrayList; import java.util.Collection; import java.util.HashMap; import java.util.HashSet; import java.util.List; import java.util.Map; import java.util.Set; import java.util.stream.Collectors; public class UndirectedGraph> extends Graph { private Map> graph; /** * This is the constructor. * Please do not change it. */ public UndirectedGraph() { this.graph = new HashMap(); } /* ** * @return true if graph is empty, false otherwise. */ public boolean isEmpty() { // TODO: Complete this method // Hint: An empty graph contains zero vertices return true; // this line needs to be rewritten } /** * @return the size (i.e. number of vertices) of this graph */ public int getSize() { // TODO: compute the size return 0; // this line needs to be rewritten } public abstract class Graph> { /** * * @return true if this graph is empty; otherwise return false */ public abstract boolean isEmpty(); /** * * @return the number of vertices of the graph */ public abstract int getSize(); /** * adds a new vertex to the graph * * * @param vertex, object of type T, if not already in this graph, is added to the graph * @throws VertexExistsException thrown if vertex already exists in the graph */ *