How can i calculate the distance between two gps points in Java?

Question

I used this code but it doesnt work:

Need the distance between two gps coordinates like 41.1212, 11.2323 in kilometers (Java)

double d2r = (180 / Math.PI);
double distance = 0;

try{
    double dlong = (endpoint.getLon() - startpoint.getLon()) * d2r;
    double dlat = (endpoint.getLat() - startpoint.getLat()) * d2r;
    double a =
        Math.pow(Math.sin(dlat / 2.0), 2)
            + Math.cos(startpoint.getLat() * d2r)
            * Math.cos(endpoint.getLat() * d2r)
            * Math.pow(Math.sin(dlong / 2.0), 2);
    double c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));
    double d = 6367 * c;

    return d;

} catch(Exception e){
    e.printStackTrace();
}