Question

Hello, i am working on java program which implements Graph as an adjacency list structure. code is the implementation of RailNetwork.
i need help to change the code so it could hold String instead of integers. so, for example, Station "Station name" is connected to "Station name"

and also i need to add class edge which basically will be a direction for those give stations. so the output will be like

"Station name" is connected to "Station name" with "this direction" (north line for example)

Thank you

import java.util.LinkedList;

// Undirected graph reprsenting rail network
public class RailNetwork {
int station; // number of stations
LinkedList railLinks[]; // Adjacency List for rail links between stations

// constructor
public RailNetwork(int station) {
this.station = station;
railLinks = new LinkedList[station];
for (int i = 0; i < station ; i++) {
railLinks[i] = new LinkedList<>(); // initialize linked lists representing rail links
}
}

// function to add rail links between source station and destionation station in both directions
public void addRailLink(int sourceStaion, int destinationStaion){

railLinks[sourceStaion].addFirst(destinationStaion); //add rail link from source station to destination station

//add back rail link from source station to destination station
railLinks[destinationStaion].addFirst(sourceStaion);
}

// function to print rail network
public void printRailNetwork(){
for (int k = 0; k < station ; k++) {
if(railLinks[k].size() > 0) { // if size of raillinks is greater than zero loop throught them to print
for (int l = 0; l < railLinks[k].size(); l++) {
System.out.print("Station " + k + " is connected to: ");
System.out.println(railLinks[k].get(l) + " "); // print rail link
}
System.out.println();
}
}
}

public static void main(String[] args) {
RailNetwork railNetwork = new RailNetwork(5); // a railnetwork object of 5 stations
railNetwork.addRailLink(1,2); // add rail link between 1 and 2
railNetwork.addRailLink(1,3); // add rail link between 1 and 3
railNetwork.addRailLink(2,4); // add rail link between 2 and 4
railNetwork.addRailLink(2,0); // add rail link between 2 and 0
railNetwork.addRailLink(2,3); // add rail link between 2 and 3
railNetwork.addRailLink(4,0); // add rail link between 4 and 0
railNetwork.addRailLink(0,3); // add rail link between 0 and 3
railNetwork.printRailNetwork(); // print rail network
}
}

output

Station 0 is connected to: 3
Station 0 is connected to: 4
Station 0 is connected to: 2

Station 1 is connected to: 3
Station 1 is connected to: 2

Station 2 is connected to: 3
Station 2 is connected to: 0
Station 2 is connected to: 4
Station 2 is connected to: 1

Station 3 is connected to: 0
Station 3 is connected to: 2
Station 3 is connected to: 1

Station 4 is connected to: 0
Station 4 is connected to: 2

Answer 1

import java.util.LinkedList;

// Undirected graph reprsenting rail network
public class RailNetwork {
   int station; // number of stations
   LinkedList railLinks[]; // Adjacency List for rail links between stations
   String[] stationNamesArray;

   // constructor
   public RailNetwork(int station) {
       this.station = station;
       railLinks = new LinkedList[station + 1];
       stationNamesArray = new String[station + 1];
       for (int i = 0; i <= station; i++) {
           stationNamesArray[i] = "empty";
           railLinks[i] = new LinkedList<>(); // initialize linked lists representing rail links
       }
   }

   // function to add rail links between source station and destionation station in
   // both directions
   public void addRailLink(String sourceStation, String destinationStation, String direction) {

       int sourceStationIndex = getStationIndex(sourceStation);

       if (sourceStationIndex < 0 && sourceStationIndex > -100000000) {
           stationNamesArray[-sourceStationIndex] = sourceStation;
           sourceStationIndex = Math.abs(sourceStationIndex);
       }

       int destinationStationIndex = getStationIndex(destinationStation);

       if (destinationStationIndex < 0 && destinationStationIndex > -100000000) {
           stationNamesArray[-destinationStationIndex] = destinationStation;
           destinationStationIndex = Math.abs(destinationStationIndex);
       }

       railLinks[sourceStationIndex].addFirst(new Edge(destinationStationIndex, direction)); // add rail link
                                                                                              
       railLinks[destinationStationIndex].addFirst(new Edge(sourceStationIndex, getOppositeDirection(direction))); // add backward link
                                                                                                              
   }

// function to get station index
   public int getStationIndex(String stationName) {
       for (int i = 1; i < stationNamesArray.length; i++) {
           if (stationNamesArray[i] == stationName)
               return i;
           if (stationNamesArray[i] == "empty")
               return -i;
       }

       return -100000000;
   }

  
// function to get backward direction for back link
   private String getOppositeDirection(String direction) {

       switch (direction) {

       case "North":
           return "South";
       case "north":
           return "south";
       case "South":
           return "North";
       case "south":
           return "north";
       case "East":
           return "West";
       case "east":
           return "west";
       case "West":
           return "East";
       case "west":
           return "east";
       default:
           return "wrong direction";

       }
   }

   // function to print rail network
   public void printRailNetwork() {
       for (int k = 1; k <= station; k++) {
           if (railLinks[k].size() > 0) { // if size of raillinks is greater than zero loop throught them to print
               for (int l = 0; l < railLinks[k].size(); l++) {
                   System.out.print("Station " + stationNamesArray[k] + " is connected to: ");
                   System.out.println(stationNamesArray[((Edge) railLinks[k].get(l)).getVertex()] + " in "
                           + ((Edge) railLinks[k].get(l)).getDirection() + " Line"); // print rail link
               }
               System.out.println();
           }
       }
   }

   public static void main(String[] args) {
       RailNetwork railNetwork = new RailNetwork(5); // a railnetwork object of 5 stations
       railNetwork.addRailLink("A", "B", "North"); // add rail link between 1 and 2
       railNetwork.addRailLink("A", "C", "South"); // add rail link between 1 and 3
       railNetwork.addRailLink("B", "D", "West"); // add rail link between 2 and 4
       railNetwork.addRailLink("B", "F", "East"); // add rail link between 2 and 0
       railNetwork.addRailLink("B", "C", "West"); // add rail link between 2 and 3
       railNetwork.addRailLink("D", "F", "North"); // add rail link between 4 and 0
       railNetwork.addRailLink("F", "C", "East"); // add rail link between 0 and 3
       railNetwork.printRailNetwork(); // print rail network
   }

   class Edge {
       int vertex;
       String direction;

       Edge(int vertex, String direction) {
           this.vertex = vertex;
           this.direction = direction;
       }

       public int getVertex() {
           return vertex;
       }

       public String getDirection() {
           return direction;
       }
   }
}

// Ouptut