Question

Exercise 1 Adjacency Matrix In this part, you will implement the data model to represent a graph. Implement the following classes Node.java: This class represents a vertex in the graph. It has only a single instance variable of type int which is set in the constructor. Implement hashCode() and equals(..) methods which are both based on the number instance variable Node - int number +Node(int number); +int getNumberO; +int hashCode() +boolean equals(Object o) +String toString0) Edge.java: This class represents a single edge in the graph consisting of the starting node, end node, and weight of the edge. The Edge must have all methods in the following class diagram. Implement hashCode() and equals(..) methods which are both based on the from, to, and weight instance variables Edge Node from - Node to; - int weight; +Edge(Node from, Node to, int weight) +Node getFromO +Node getToO +int getWeight0) +int hashCode0) +boolean equals(Object o) +String toString0 Graph.java: This class has only one instance variable that stores a two-dimensional integer array. This array represents an adjacency matrix that can represent any weighted directed graph. Implement two constructors the default constructor initializes the array to represent the graph below the second constructor expects a two dimensional array as argument and initializes the instance variable array to it. Graph intII matrix +GraphO +Graph(int[IJl] adjacencyMatrix) +boolean hasEdge(Node from, Node to) tint weight(Node from, Node to) +List-Edge> getOutgoingEdges(Node from) +List Node> getNodes) 4 0 5 6String toString0 The Graph class must have all methods in the following class diagram. A description for each method is given below Below is a description for each of the functions inside the Graph class Checks if an edge exists Hint:the value in the instance variable array at [from] [to] is not 0 public boolean hasEdge(Node from, Node to) Returns the weight of the specified edge *Hint: Return the value in the instance variable array at [from]Cto] ereturn Weight if edge exists, 0 if no edge exists public int weight (Node from, Node to) Returns a list of outgoing edges that start at the given node Hint: Loop through the row at from and create an edge for each column with *from-row, to-column, weight-[row] [column] public List getOutgoingEdges(Node from) Returns a list of all nodes in the graph Hint: Use a loop from 0 to instance array.length to create the nodes public List getNodesO

Answer 1

Node.java

public class Node {
   private int number;
   //constructor
   public Node(int number)
   {
       this.number=number;
   }
   //method to return node number
   public int getNumber()
   {
       return number;
   }
   //hashcode method
   @Override
   public int hashCode() {
       final int prime = 31;
       int result = 1;
       result = prime * result + number;
       return result;
   }
   //equals method
   @Override
   public boolean equals(Object obj) {
       Node other=(Node)obj;
       if (number != other.getNumber())
           return false;
       else
           return true;
   }
   //to string method
   @Override
   public String toString() {
       return "Node [number=" + number + "]";
   }
}

Edge.java

public class Edge {
   private Node from;
   private Node to;
   int weight;
   //constructor
   public Edge(Node from, Node to, int weight) {
       super();
       this.from = from;
       this.to = to;
       this.weight = weight;
   }
   /**
   * @return the from
   */
   public Node getFrom() {
       return from;
   }
   /**
   * @return the to
   */
   public Node getTo() {
       return to;
   }
   /**
   * @return the weight
   */
   public int getWeight() {
       return weight;
   }
   //hashcode method
   @Override
   public int hashCode() {
       final int prime = 31;
       int result = 1;
       result = prime * result + ((from == null) ? 0 : from.hashCode());
       result = prime * result + ((to == null) ? 0 : to.hashCode());
       result = prime * result + weight;
       return result;
   }
   //equals method
   @Override
   public boolean equals(Object obj) {
       Edge other = (Edge) obj;
       if (from == null) {
           if (other.from != null)
               return false;
       } else if (!from.equals(other.from))
           return false;
       if (to == null) {
           if (other.to != null)
               return false;
       } else if (!to.equals(other.to))
           return false;
       if (weight != other.weight)
           return false;
       return true;
   }
   @Override
   public String toString() {
       return "Edge [from=" + from + ", to=" + to + ", weight=" + weight + "]";
   }
  

}

Graph.java

import java.util.ArrayList;
import java.util.List;

public class Graph {
   private int[][] matrix;
   //default constructor
   public Graph()
   {
       //adijency matrix based on the graph
       int i[][]={{0,5,2,0,0,0,0},{5,0,0,1,0,0,0},{2,0,0,2,0,0,8},{0,1,2,0,2,1,0},{0,0,0,2,0,0,3},{0,0,0,1,0,0,0},{0,0,8,0,3,0,0}};
       matrix=new int[7][7];
       for(int j=0;j<7;j++)
           for(int k=0;k<7;k++)
               matrix[j][k]=i[j][k];
   }
   //constructor to initialize the matrix
   public Graph(int[][] matrix) {
       super();
       this.matrix = matrix;
   }
   //method to detect the is edge is present or not
   public boolean hasEdge(Node from,Node to)
   {
       if(matrix[from.getNumber()][to.getNumber()]==0)
       {
           return false;
       }
       else
       {
           return true;
       }
   }
   //method to return the weight of the graph
   public int weight(Node from,Node to)
   {
       return matrix[from.getNumber()][to.getNumber()];
   }
   //method to return this list of outgoing edges
   public List<Edge> getOutgoingEdges(Node from)
   {
       List<Edge> li=new ArrayList<Edge>();
       int j=from.getNumber();
       for(int i=0;i<matrix[j].length;i++)
       {
           if(matrix[j][i]!=0)
           {
               li.add(new Edge(new Node(j),new Node(i),matrix[i][j]));
           }
       }
       return li;
      
   }
   //method to return the list of nodes
   public List<Node> getNodes()
   {
       List<Node> li=new ArrayList<Node>();
       for(int i=0;i<matrix.length;i++)
       {
           li.add(new Node(i));
       }
       return li;
      
   }

}

//sample driver class

import java.util.List;

public class Demo {
   public static void main(String args[])
   {
       Graph ob=new Graph();
       List<Node> li=ob.getNodes();

      //to print list for nodes
       System.out.println(li);
       List<Edge>oe=ob.getOutgoingEdges(new Node(4));

   //to print the edges
       System.out.println(oe);
   }

}

output:

<terminated> Demo [Java Application]/usr/lib/jvm/java-11-oracle/bin/java (30-May-2019, 11:14:32 am) [Node [number-0], Node [number-1], Node [number 2], Node [number-3], Node [number 4], Node [number-5], Node [number-6]] [Edge [from=Node [number-4], to-Node [number-3], weight-2], Edge [from-Node [number-4], to-Node [number-6], weight-311

if you have any doubt are any changes in the program please do comment..