Exception in thread error

Question

I got the following code:
import java.io.*;
import java.util.*;
public class BranchB2
     public static void main(String[] args)
          int pathCost, source, destination, count=0;
          int userSource, userDestination;
          String tempRead;
          ArrayList edge = new ArrayList();
          System.out.print("Start: ");
          userSource = read();
          System.out.print("End: ");
          userDestination = read();
          if(userSource == -1 || userDestination == -1)
               System.out.println("Error in entry, Program will now exit!");
               System.exit(0);
        try
               FileReader file = new FileReader("graph_info - TUTE 2.txt");
               BufferedReader fileInput = new BufferedReader(file);
               StringTokenizer st = new StringTokenizer(fileInput.readLine());
               while (st.hasMoreTokens())
                    source = Integer.parseInt(st.nextToken());
                    destination = Integer.parseInt(st.nextToken());
                    pathCost = Integer.parseInt(st.nextToken());
                    edge.add(new Edge(pathCost, source, destination));
                    count++;
                    st = new StringTokenizer(fileInput.readLine()); //Go to next line
                    System.out.println("TEST" + count);
               System.out.println("TEST");
               System.out.println("");     
               System.out.println("Number of lines in file is " + count);
          catch (IOException e)
               System.out.println("ERROR: Cannot Read File!");
          System.out.println("TEST");          
     public static int read()
          int value = -1;
          try
               InputStreamReader isr = new InputStreamReader(System.in);
               BufferedReader br = new BufferedReader(isr);
               String tempRead = br.readLine();
               value = Integer.parseInt(tempRead);
          catch (IOException e)
               System.out.println("ERROR: Cannot read keyboard!");
          return value;
}File:
1 2 2
1 3 4
2 4 5
3 6 5
4 5 3
5 7 2
4 8 5
8 9 2
8 13 13
13 15 3
13 14 1
6 10 8
10 11 4
10 12 2
10 2 2
11 14 2
14 15 4
11 11 11When i run it, i get the following error:
C:\Users\Taurus\Desktop\University\AMI - 4517\Assignment\branchb>java BranchB2
Start: 2
End: 1
TEST1
TEST2
TEST3
TEST4
TEST5
TEST6
TEST7
TEST8
TEST9
TEST10
TEST11
TEST12
TEST13
TEST14
TEST15
TEST16
TEST17
TEST18
Exception in thread "main" java.lang.NullPointerException
        at java.util.StringTokenizer.<init>(Unknown Source)
        at java.util.StringTokenizer.<init>(Unknown Source)
        at BranchB2.main(BranchB2.java:37)
C:\Users\Taurus\Desktop\University\AMI - 4517\Assignment\branchb>What can I do to fix it?

Answer 1

I'm guessing that the objective of this program is to read each line from "graph_info - TUTE 2.txt" and convert it into an Edge object. If that is the case, then what did you expect this piece of code will do?
StringTokenizer st = new StringTokenizer(fileInput.readLine());
while (st.hasMoreTokens())
  source = Integer.parseInt(st.nextToken());
  destination = Integer.parseInt(st.nextToken());
  pathCost = Integer.parseInt(st.nextToken());
  edge.add(new Edge(pathCost, source, destination));
  count++;
  st = new StringTokenizer(fileInput.readLine()); //Go to next line
  System.out.println("TEST" + count);
}I would write it like this.
String str = "";
while ( (str = fileInput.readLine()) != null )//Read every line until EOF
  String []splits = str.split(" ");//No need for StringTokenizer
  source = Integer.parseInt(splits[0]);
  destination = Integer.parseInt(splits[1]);
  pathCost = Integer.parseInt(splits[2]);
  edge.add(new Edge(pathCost, source, destination));
  count++;
  System.out.println("TEST" + count);
}