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  • creating objects from trivial graph format text file. java. dijkstra algorithm.

    - by user560084
    i want to create objects, vertex and edge, from trivial graph format txt file. one of programmers here suggested that i use trivial graph format to store data for dijkstra algorithm. the problem is that at the moment all the information, e.g., weight, links, is in the sourcecode. i want to have a separate text file for that and read it into the program. i thought about using a code for scanning through the text file by using scanner. but i am not quite sure how to create different objects from the same file. could i have some help please? the file is v0 Harrisburg v1 Baltimore v2 Washington v3 Philadelphia v4 Binghamton v5 Allentown v6 New York # v0 v1 79.83 v0 v5 81.15 v1 v0 79.75 v1 v2 39.42 v1 v3 103.00 v2 v1 38.65 v3 v1 102.53 v3 v5 61.44 v3 v6 96.79 v4 v5 133.04 v5 v0 81.77 v5 v3 62.05 v5 v4 134.47 v5 v6 91.63 v6 v3 97.24 v6 v5 87.94 and the dijkstra algorithm code is Downloaded from: http://en.literateprograms.org/Special:Downloadcode/Dijkstra%27s_algorithm_%28Java%29 */ import java.util.PriorityQueue; import java.util.List; import java.util.ArrayList; import java.util.Collections; class Vertex implements Comparable<Vertex> { public final String name; public Edge[] adjacencies; public double minDistance = Double.POSITIVE_INFINITY; public Vertex previous; public Vertex(String argName) { name = argName; } public String toString() { return name; } public int compareTo(Vertex other) { return Double.compare(minDistance, other.minDistance); } } class Edge { public final Vertex target; public final double weight; public Edge(Vertex argTarget, double argWeight) { target = argTarget; weight = argWeight; } } public class Dijkstra { public static void computePaths(Vertex source) { source.minDistance = 0.; PriorityQueue<Vertex> vertexQueue = new PriorityQueue<Vertex>(); vertexQueue.add(source); while (!vertexQueue.isEmpty()) { Vertex u = vertexQueue.poll(); // Visit each edge exiting u for (Edge e : u.adjacencies) { Vertex v = e.target; double weight = e.weight; double distanceThroughU = u.minDistance + weight; if (distanceThroughU < v.minDistance) { vertexQueue.remove(v); v.minDistance = distanceThroughU ; v.previous = u; vertexQueue.add(v); } } } } public static List<Vertex> getShortestPathTo(Vertex target) { List<Vertex> path = new ArrayList<Vertex>(); for (Vertex vertex = target; vertex != null; vertex = vertex.previous) path.add(vertex); Collections.reverse(path); return path; } public static void main(String[] args) { Vertex v0 = new Vertex("Nottinghill_Gate"); Vertex v1 = new Vertex("High_Street_kensignton"); Vertex v2 = new Vertex("Glouchester_Road"); Vertex v3 = new Vertex("South_Kensignton"); Vertex v4 = new Vertex("Sloane_Square"); Vertex v5 = new Vertex("Victoria"); Vertex v6 = new Vertex("Westminster"); v0.adjacencies = new Edge[]{new Edge(v1, 79.83), new Edge(v6, 97.24)}; v1.adjacencies = new Edge[]{new Edge(v2, 39.42), new Edge(v0, 79.83)}; v2.adjacencies = new Edge[]{new Edge(v3, 38.65), new Edge(v1, 39.42)}; v3.adjacencies = new Edge[]{new Edge(v4, 102.53), new Edge(v2, 38.65)}; v4.adjacencies = new Edge[]{new Edge(v5, 133.04), new Edge(v3, 102.53)}; v5.adjacencies = new Edge[]{new Edge(v6, 81.77), new Edge(v4, 133.04)}; v6.adjacencies = new Edge[]{new Edge(v0, 97.24), new Edge(v5, 81.77)}; Vertex[] vertices = { v0, v1, v2, v3, v4, v5, v6 }; computePaths(v0); for (Vertex v : vertices) { System.out.println("Distance to " + v + ": " + v.minDistance); List<Vertex> path = getShortestPathTo(v); System.out.println("Path: " + path); } } } and the code for scanning file is import java.util.Scanner; import java.io.File; import java.io.FileNotFoundException; public class DataScanner1 { //private int total = 0; //private int distance = 0; private String vector; private String stations; private double [] Edge = new double []; /*public int getTotal(){ return total; } */ /* public void getMenuInput(){ KeyboardInput in = new KeyboardInput; System.out.println("Enter the destination? "); String val = in.readString(); return val; } */ public void readFile(String fileName) { try { Scanner scanner = new Scanner(new File(fileName)); scanner.useDelimiter (System.getProperty("line.separator")); while (scanner.hasNext()) { parseLine(scanner.next()); } scanner.close(); } catch (FileNotFoundException e) { e.printStackTrace(); } } public void parseLine(String line) { Scanner lineScanner = new Scanner(line); lineScanner.useDelimiter("\\s*,\\s*"); vector = lineScanner.next(); stations = lineScanner.next(); System.out.println("The current station is " + vector + " and the destination to the next station is " + stations + "."); //total += distance; //System.out.println("The total distance is " + total); } public static void main(String[] args) { /* if (args.length != 1) { System.err.println("usage: java TextScanner2" + "file location"); System.exit(0); } */ DataScanner1 scanner = new DataScanner1(); scanner.readFile(args[0]); //int total =+ distance; //System.out.println(""); //System.out.println("The total distance is " + scanner.getTotal()); } }

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