package Sorting_DAG.dataaccess;

import java.util.*;

public abstract class AbstractGraph<V> implements Graph<V> {

//fields
protected List<V> vertices = new ArrayList<>(); // Store vertices
protected List<List<Edge>> neighbors
         = new ArrayList<>(); // Adjacency lists

/**
* Construct an empty graph
*/
protected AbstractGraph() {
}

/**
* Construct a graph from vertices and edges stored in arrays
*/
protected AbstractGraph(V[] vertices, int[][] edges) {
   for (int i = 0; i < vertices.length; i++) {
         addVertex(vertices[i]);
   }

   createAdjacencyLists(edges, vertices.length);
}

/**
* Construct a graph from vertices and edges stored in List
*/
protected AbstractGraph(List<V> vertices, List<Edge> edges) {
   for (int i = 0; i < vertices.size(); i++) {
         addVertex(vertices.get(i));
   }

   createAdjacencyLists(edges, vertices.size());
}

/**
* Construct a graph for integer vertices 0, 1, 2 and edge list
*/
protected AbstractGraph(List<Edge> edges, int numberOfVertices) {
   for (int i = 0; i < numberOfVertices; i++) {
         addVertex((V) (new Integer(i))); // vertices is {0, 1, ...}
   }
   createAdjacencyLists(edges, numberOfVertices);
}

/**
* Construct a graph from integer vertices 0, 1, and edge array
*/
protected AbstractGraph(int[][] edges, int numberOfVertices) {
   for (int i = 0; i < numberOfVertices; i++) {
         addVertex((V) (new Integer(i))); // vertices is {0, 1, ...}
   }
   createAdjacencyLists(edges, numberOfVertices);
}

/**
* Create adjacency lists for each vertex
*/
private void createAdjacencyLists(
         int[][] edges, int numberOfVertices) {
   for (int i = 0; i < edges.length; i++) {
         addEdge(edges[i][0], edges[i][1]);
   }
}

/**
* Create adjacency lists for each vertex
*/
private void createAdjacencyLists(
         List<Edge> edges, int numberOfVertices) {
   for (Edge edge : edges) {
         addEdge(edge.u, edge.v);
   }
}

Hashtables from scratch Create a file called Lab4-XXXXXXXX.py...