Here I downloaded data of places from a server via script, now I want to sort the list of Place in ascending order of distance using Pythagore

private class chargeur extends AsyncTask<Void, Void, List<Place>> {

        @Override
        protected List<Place> doInBackground(Void... voids) {
            List<Place> pl = new ArrayList<>();
            URL adresse = null;

            try {
                HttpsURLConnection cnx = Connecteur.connecter("get_all_places.php");
                BufferedReader B = new BufferedReader(new InputStreamReader(cnx.getInputStream()));
                String reponse = "";
                String lign = "";
                while ((lign = B.readLine())!=null) {
                    reponse+= lign;
                }

                JSONArray tab = new JSONArray(reponse);
                for (int i = 0; i<tab.length();i++) {
                    JSONObject obj = tab.getJSONObject(i);
                    String name = obj.getString("name");
                    String longitude = obj.getString("longitude");
                    String latitude = obj.getString("latitude");
                    Place p = new Place(name, longitude ,latitude);
                    pl.add(p);
                }
                return pl;
            } catch (Exception e) {}
        }
        // ...
}

2 Answers

0
forpas On Best Solutions

You can use hypot() which returns the distance of 2 points from java.lang.Math class:

Collections.sort(pl, new Comparator<Place>() {
    public int compare(Place pl1, Place pl2) {
        Double d1 = Math.hypot(Double.parseDouble(p1.getLongitude()), Double.parseDouble(p1.getLatitude()));
        Double d2 = Math.hypot(Double.parseDouble(p2.getLongitude()), Double.parseDouble(p2.getLatitude()));
        return  d1.compareTo(d2);
    }
});
1
anatoli On

You could make it like

Collections.sort(pl, new Comparator<Place>() {
    public int compare(Place pl1, Place pl2) {
        // Write your logic here.
        return Math.sqrt(pl1.longitude * pl1.longitude + pl1.latitude * pl1.latitude) < 
            Math.sqrt(pl2.longitude * pl2.longitude + pl2.latitude * pl2.latitude);
    }});