I am inputting an adjacency list for a graph. There are three columns of data (vertex, destination, edge) separated by a single space. Here is my implementation so far:

         FileStream in = new FileStream("input1.txt");
         Scanner s = new Scanner(in);

         String buffer;
         String [] line = null;
        while (s.hasNext()) 
        {       
            buffer = s.nextLine();
            line = buffer.split("\\s+");     
            g.add(line[0]);
            System.out.println("Added vertex " + line[0] + ".");
            g.addEdge(line[0], line[1], Integer.parseInt(line[2]));
            System.out.println("Added edge from " + line[0] + " to " + line[1] + " with a weight of " + Integer.parseInt(line[2]) + ".");                  
         }

         System.out.println("Size of graph = " + g.size());

Here is the output:

Added vertex a.
Added edge from a to b with a weight of 9.
Exception in thread "main" java.lang.NullPointerException
    at structure5.GraphListDirected.addEdge(GraphListDirected.java:93)
    at Driver.main(Driver.java:28)

I was under the impression that

 line = buffer.split("\\s+");

would return a 2 dimensional array of Strings to the variable line. It seemed to work the first time but not the second. Any thoughts?

I would also like some feedback on my implementation of this problem. Is there a better way? Anything to help out a novice! :)