Calculer distance euclidienne

import java.awt.Point;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.List;
import java.util.stream.Collectors;

class Ville {
    final int id;
    final double x, y;

    Ville(String str) {
        String[] tab = str.split(",");
        id = Integer.parseInt(tab[0]);
        x = Double.parseDouble(tab[1]);
        y = Double.parseDouble(tab[2]);
    }
}

class Parcours {
    final int a, b;
    final double distance;

    Parcours(Ville a, Ville b) {
        this.a = a.id;
        this.b = b.id;
        distance = Point.distance(a.x, a.y, b.x, b.y);
    }

    public String toString() {
        return String.format("(%d,%d)=%f", a, b, distance);
    }
}

public class Test{

    public static void main(String[] args) throws Exception {
        List<Ville> villes = Files.lines(Paths.get("C:/test.txt")).skip(1)
                .map(Ville::new).collect(Collectors.toList());
        List<Parcours> parcours = villes.stream().flatMap(a ->
                villes.stream().map(b -> new Parcours(a, b)))
            .collect(Collectors.toList());
        System.out.println(parcours);
    }
}

[(0,0)=0,000000, (0,1)=5,301141, (0,2)=9,036998,
 (1,0)=5,301141, (1,1)=0,000000, (1,2)=14,021260,
 (2,0)=9,036998, (2,1)=14,02126, (2,2)=0,000000]

filter(b -> a.id < b.id)

[(0,1)=5,301141, (0,2)=9,036998, (1,2)=14,021260]