taking input from file using scanner class in java

Question

I am trying store a list of cities in a class using two co-ordinates(x,y) in java

My class is as follows:

public class City {
    int x;
    int y;

    // Constructs a city at chosen x, y location
    public City(int x, int y){
        this.x = x;
        this.y = y;
    }
}

I have made another class to store the cities in an ArrayList :

public class TourManager {

    // Holds our cities
    private static ArrayList destinationCities = new ArrayList<City>();

    // Adds a destination city
    public static void addCity(City city) {
        destinationCities.add(city);
    }
}

My main class is as follows:

public class Final {
    public static void main(String[] args) {
        // Create and add our cities
        City city = new City(60, 200);
        TourManager.addCity(city);
        City city2 = new City(180, 200);
        TourManager.addCity(city2);
        City city3 = new City(80, 180);
        TourManager.addCity(city3);
    }
}

Here, I have stored three cities in the ArrayList inside the main function. But now I want to take the input from a file in the following format. I just want to take the co-ordinates ignoring all other lines.

NAME: sample.tsp

TYPE: TSP

COMMENT: Odyssey of Ulysses (Groetschel/Padberg)

DIMENSION: 3

EDGE_WEIGHT_TYPE: GEO

NODE_COORD_SECTION

1 60 200

2 180 200

3 80 180

I want to use the scanner class to take the input but getting confused in using it. i have made a partial code fragment to take input but it isn't working:

Scanner in = new Scanner(new File("sample.tsp"));
String line = "";
int n;
in.nextLine();
in.nextLine();
in.nextLine();
line = in.nextLine();
line = line.substring(11).trim();
n = Integer.parseInt(line);
in.nextLine();
in.nextLine();

But how will I take the coordinates using the City class object as I have done before from this file?

Answer 1

You need to skip the first few lines, which you don't need.

Then split the lines to get the various numbers. Index 0 contains the serial no., 1 and 2 contain the coordinates. Then parse them to int . eg:

in.nextLine();// multiple times.
//...
String cs = in.nextLine(); // get the line
City city = new City(Integer.parseInt(cs.split(" ")[1]), Integer.parseInt(cs.split(" ")[2]));
TourManager.addCity(city);

String cs2 = in.nextLine();
City city2 = new City(Integer.parseInt(cs2.split(" ")[1]), Integer.parseInt(cs2.split(" ")[2]));
TourManager.addCity(city2);

String cs3 = in.nextLine();
City city3 = new City(Integer.parseInt(cs3.split(" ")[1]), Integer.parseInt(cs3.split(" ")[2]));
TourManager.addCity(city3);

Answer 2

Whenever you use in.nextLine() , actually it takes the string that you entered. So try to assign it to some string variable. For example:

String s =in.nextLine();

Also, just using in.nextLine(); which you did in 2nd,3rd 4th,8th and 9th line is not needed.