get distance between two geo points

 private static int EARTH_RADIUS_KM = 6371;

    public static int MILLION = 1000000;

    /**
     * Computes the distance in kilometers between two points on Earth.
     *
     * @param lat1 Latitude of the first point
     * @param lon1 Longitude of the first point
     * @param lat2 Latitude of the second point
     * @param lon2 Longitude of the second point
     * @return Distance between the two points in kilometers.
     */
    public static double distanceKm(double lat1, double lon1, double lat2, double lon2) {
        double lat1Rad = Math.toRadians(lat1);
        double lat2Rad = Math.toRadians(lat2);
        double deltaLonRad = Math.toRadians(lon2 - lon1);
     
        return Math.acos(Math.sin(lat1Rad) * Math.sin(lat2Rad) + Math.cos(lat1Rad) * Math.cos(lat2Rad)
                * Math.cos(deltaLonRad))
                * EARTH_RADIUS_KM;
    }