Path Finder in a java programe

PathFinder.java

public class PathFinder

{

private ST  prev = new ST();

 private ST dist = new ST();

              public PathFinder(Graph G, String s

           {

                   Queue q = new Queue();

        q.enqueue(s);

        dist.put(s, 0);

       

        while (!q.isEmpty())

{

            String v = q.dequeue();

            for (String w : G.adjacentTo(v))

{

                if (!dist.contains(w))

{

                    q.enqueue(w);

                    dist.put(w, 1 + dist.get(v));

                    prev.put(w, v);

                }

            }

        }

    }

    public boolean isReachable(String v)

{

        return dist.contains(v);

    }

    public int distanceTo(String v)

{

        if (!dist.contains(v)) return Integer.max_value;

        return dist.get(v);

    }

    public Iterable pathTo(String v)

{

        Stack path = new Stack();

        while (v != null && dist.contains(v))

{

            path.push(v);

            v = prev.get(v);

     }

        return path;

    }

                     public static void main(String[] args)

              {

        String filename  = args[0];

        String delimiter = args[1];

        In in = new In(filename);

        Graph G = GraphGenerator.read(in, delimiter);

        String s = args[2];

        PathFinder pf = new PathFinder(G, s);

        while (!StdIn.isEmpty())

 {

            String t = StdIn.readLine();

            for (String v : pf.pathTo(t))

{

                StdOut.println("   " + v);

        }

            StdOut.println("distance " + pf.distanceTo(t));

        }

    }

            }