Access the value of the pair in the ArrayList

Question

How can I pass the the last added element to the ArrayList and the i element in the ArrayList to the haversineDistance method and how can I get the lat1, lat2, long1 and long2 from them in the haversineDistance method?

I want to iterate through the list to figure out whether the sender of the request is located close to one element in the list.

Test class:

@Path("/test")

public class Test {

    private static ArrayList<LatLong> latLongList = new ArrayList<>();

    @POST
    @Consumes(MediaType.APPLICATION_JSON)
    public Response storeData(Data data) {

        String macD = data.getMac();
        int routeD = data.getRoute();
        float latD = data.getLatitude();
        float longD = data.getLongitude();

        // Add the lat and Long to the ArrayList.
        latLongList.add(new LatLong(latD, longD));

        int size = latLongList.size();
        if (size > 1) {

            for (int i = 0; i < latLongList.size(); i++) {

                double distance = haversineDistance(latLongList.get(i),
                        latLongList.get(latLongList.size() - 1));
                if (distance > 4) {
                    processData(macD, routeD, latD, longD);
                } else {
                    return null;
                }
            }
        } else {

            processData(macD, routeD, latD, longD);
        }

        return Response.status(201).build();
    }

    private void processData(String macD, int routeD, float latD, float longD) {
        Database db = new Database();
        db.insertData(macD, routeD, latD, longD);
    }

    private double haversineDistance(ArrayList<LatLong> x, ArrayList<LatLong> y) {
        return 0;

    }

}

Answer 1

If you want your method haversineDistance to compute the distance between two points , you should design the method to accept two points , not two ArrayList of points . As a point is represented by a LatLong object, you should change the method to:

private double haversineDistance(LatLong x, LatLong y) {
    double xLat = x.getLatitude();
    double xLng = x.getLongitude();
    double yLat = y.getLatitude();
    double yLng = y.getLongitude();

    // compute haversine distance
    double d = ...;

    return d;
}