InstanceFile.java

package cph.instance;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.StringTokenizer;

public record InstanceFile(String fileName, String name, String type) {

    public Instance loadInstance() throws IOException, FormatException {
        String resourcePath = "/instances/" + fileName;
        InputStream inputStream = InstanceFile.class.getResourceAsStream(resourcePath);
        if (inputStream == null) {
            throw new IOException("Resource not found in the classpath: " + resourcePath);
        }

        return loadInstance(name, inputStream);
    }

    private Instance loadInstance(String name, InputStream inputStream) throws IOException, FormatException {
        try (var br = new BufferedReader(new InputStreamReader(inputStream))) {
            String line = br.readLine();
            if (line == null) {
                throw new FormatException("The file is empty");
            }

            StringTokenizer header = new StringTokenizer(line);
            int numNodes = Integer.parseInt(header.nextToken());
            if (header.countTokens() < 2) {
                throw new FormatException("The first line must contain the number of nodes, "
                        + "the number of hubs and the capacity of each hub");
            }
            int numHubs = Integer.parseInt(header.nextToken());
            int hubCapacity = Integer.parseInt(header.nextToken());

            int[][] nodeData = new int[numNodes][3];

            line = br.readLine();
            while (line != null && !line.isBlank()) {
                StringTokenizer st = new StringTokenizer(line);
                int node = Integer.parseInt(st.nextToken());
                int x = Integer.parseInt(st.nextToken());
                int y = Integer.parseInt(st.nextToken());
                int demand = Integer.parseInt(st.nextToken());

                nodeData[node][0] = x;
                nodeData[node][1] = y;
                nodeData[node][2] = demand;
                line = br.readLine();
            }

            return new Instance(name, numNodes, numHubs, hubCapacity, nodeData);
        } catch (NumberFormatException e) {
            throw new FormatException("Invalid file format");
        }
    }

    @Override
    public String toString() {
        return "Name: " + name + " FileName:" + fileName;
    }

}