InstanceFile.java

package cwp.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);
            header.nextToken();
            int numVertices = Integer.parseInt(header.nextToken());
            if (!header.hasMoreTokens()) {
                throw new FormatException(
                        "The first line must contain the number of vertices (duplicated) and the number of edges");
            }
            int numEdges = Integer.parseInt(header.nextToken());

            int[][] weights = new int[numVertices][numVertices];

            line = br.readLine();
            while (line != null) {
                StringTokenizer st = new StringTokenizer(line);
                int i = Integer.parseInt(st.nextToken());
                int j = Integer.parseInt(st.nextToken());

                weights[i][j] = 1;
                weights[j][i] = 1;
                line = br.readLine();
            }

            return new Instance(name, numVertices, numEdges, weights);
        } catch (NumberFormatException e) {
            throw new FormatException("Invalid file format");
        }
    }

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

}