public static void main(String[] args) {

double[] a = {53.3807, -6.594596000000024}; // Maynooth University.

double[] b = {40.6892494, -74.0445004}; // Statue of Liberty.

double distance = getDistance(a, b);

System.out.println("Distance between point a (" + a[0] + "," + a[1] + ") and b (" + b[0] + "," + b[1] + ") is " + distance + "km.");

}

public static double getDistance(double[] a, double[] b) {

final int r = 6371; // Radius of the earth.

double h = haversin(Math.toRadians(b[0] - a[0])) + (Math.cos(a[0]) * Math.cos(b[0]) * haversin(Math.toRadians(b[1] - a[1])));

double d = 2 * r * Math.asin(Math.sqrt(h));

return (haversin(d/r) * 10000) / 0.62137; // Convert to Km before return.

}

public static double haversin(double rad) {

return (1 - Math.cos(rad)) / 2;

}

}