CVRPData.java

package CVRP;

import java.io.*;
import java.awt.Point;

/**
 * CVRPData.java
 *
 * This class reads in a CVRP data file and provides "get methods" to
 * access the demand and distance information. It does some
 * parameter checking to make sure that nodes passed to the get
 * methods are within the valid range.
 *
 * It should be initialised by calling readFile(). 
 *
 * @author Tim Kovacs
 * @version 20/10/2013
 */

public class CVRPData {

    /** The capacity that each vehicle has */
    public static int VEHICLE_CAPACITY;

    /** The number of nodes in the fruitybun CVRP i.e. the depot and the customers */
    public static int NUM_NODES;

    /** This is only used for testing. Normally the class is initialised by calling readFile() */
    public static void main(String[] dataFileName) throws FileNotFoundException, IOException {
	if (dataFileName.length != 1)
	    quit("I need exactly 1 argument: the name of the data file to read");

	readFile(dataFileName[0]);
    }

    /** Return the demand for a given node. */
    public static int getDemand(int node) {
	if (!nodeIsValid(node)) {
	    System.err.println("Error: demand for node " + node + 
			       " was requested from getDemand() but only nodes 1.." + NUM_NODES + " exist");
	    System.exit(-1);
	}	    
	return demand[node];
    }
        
    /** Return the Euclidean distance between the two given nodes */
    public static double getDistance(int node1, int node2) {
	if (!nodeIsValid(node1)) {
	    System.err.println("Error: distance for node " + node1 + 
			       " was requested from getDistance() but only nodes 1.." + NUM_NODES + " exist");
	    System.exit(-1);
	}	    
	
	if (!nodeIsValid(node2)) {
	    System.err.println("Error: distance for node " + node2 + 
			       " was requested from getDistance() but only nodes 1.." + NUM_NODES + " exist");
	    System.exit(-1);
	}	    

	int x1 = coords[node1][X_COORDINATE];
	int y1 = coords[node1][Y_COORDINATE];
	int x2 = coords[node2][X_COORDINATE];
	int y2 = coords[node2][Y_COORDINATE];

	// compute Euclidean distance
	return Math.sqrt(Math.pow((x1-x2),2) + Math.pow((y1-y2),2));

    // For example, the distance between 33,44 and 44,13 is:
    // 33-44 = -11 and 11^2 = 121
    // 44-13 = 31 and 31^2 = 961
    // 121 + 961 = 1082
    // The square root of 1082 = 32.893768...
    }    

    //* Return the absolute co-ordinates of the given node */
    public static Point getLocation(int node) {
      if (!nodeIsValid(node)) {
	System.err.println("Error: Request for location of non-existent node " + node + ".");
	System.exit(-1);
      }

      return new Point(coords[node][X_COORDINATE], coords[node][Y_COORDINATE]);
    }

    /** Return true if the given node is within the valid range (1..NUM_NODES), false otherwise */
    private static boolean nodeIsValid(int node) {
	if (node < 1 || node > NUM_NODES)
	    return false;
	else
	    return true;
    }
    
    private static final int X_COORDINATE = 0; // x-axis coordinate is dimension 0 in coords[][]
    private static final int Y_COORDINATE = 1; // y-axis coordinate is dimension 1 in coords[][]
    private static final int NUM_COORDINATE_DIMENSIONS = 2;

    // 2-dimensional array with the coordinates of each node in the .vrp file. 
    // coords[0] is a dummy entry which is not used. Node 1 is at coords[1], node 2 is at coords[2] and so on.
    // A more Object-Oriented solution would have been to create node objects. That would probably have been better.
    private static int [][] coords;
    // 1-dimensional array with the demand for each customer
    private static int[] demand;

    private static final String DIMENSION_PREFIX = "DIMENSION : ";
    private static final String CAPACITY_PREFIX = "CAPACITY : ";

    /** Read the .vrp data file into arrays. This method does minimal format checking on the file */
    public static void readFile(String file) {	
        try {
            BufferedReader reader = new BufferedReader(new FileReader(file));
	    String input;

	    // read first line, which tells us the number of nodes in data file
	    input = reader.readLine(); 
	    if (!input.startsWith(DIMENSION_PREFIX))
		quit("Error: first line must begin with \"" + DIMENSION_PREFIX + "\"");
	    // extract the text which follows the prefix
	    input = input.substring(DIMENSION_PREFIX.length()); 
	    NUM_NODES = Integer.valueOf(input);

	    // create arrays to hold the data we will read from the file
	    // +1 because we don't use index 0
	    coords = new int[NUM_NODES+1][NUM_COORDINATE_DIMENSIONS];
	    demand = new int[NUM_NODES+1];
	    
	    // read second line, which tells us the capacity each truck has
	    input = reader.readLine(); 
	    if (!input.startsWith(CAPACITY_PREFIX))
		quit("Error: second line must begin with \"" + CAPACITY_PREFIX + "\"");
	    input = input.substring(CAPACITY_PREFIX.length()); 
	    VEHICLE_CAPACITY = Integer.valueOf(input);

	    // read line saying "NODE_COORD_SECTION
	    input = reader.readLine(); 

	    // read each node coordinate and add it to coords[][]
	    String[] words;
	    for (int node=1; node<= NUM_NODES; node++) {
		input = reader.readLine(); 	 
		words = input.split(" "); // format: node number, x-coordinate, y-coordinate
		coords[node][X_COORDINATE] = Integer.valueOf(words[1]);
		coords[node][Y_COORDINATE] = Integer.valueOf(words[2]);
		//System.out.println(node + " " + coords[node][X_COORDINATE] + " " + coords[node][Y_COORDINATE]);
	    }

	    // read line saying "DEMAND_SECTION"
	    input = reader.readLine();
	    if (!input.equals("DEMAND_SECTION"))
		quit("I expected to read DEMAND_SECTION but I found: " + input);

	    // read the demand for each node
	    for (int node=1; node<= NUM_NODES; node++) {
		input = reader.readLine(); 	 
		words = input.split(" "); // format: node number, demand
		demand[node] = Integer.valueOf(words[1]);
		//System.out.println(node + " " + demand[node]);
	    }
	    reader.close();                         	
	}
        catch(FileNotFoundException e) {
            quit("Error: unable to open file " + file);
        }
        catch(IOException e) {
            quit("Error: an I/O problem occurred attempting to read " + file);
        }   

    }
    
    /** Print an error message and shut down. */
    private static void quit(String message) {
	System.err.println(message);
	System.exit(-1);
    }

}