The distance between "Chengdu Vocational Technical College" and "Royal Garden"

GetGeo.java

/**
 * Created on 14-6-15
 *
 * output:
 * 2.787433034459691 Miles
 * 4.485938629409498 Kilometers
 * 2.4206068471247955 Nautical Miles
 *
 * Original post by dommer on StackOverflow: http://stackoverflow.com/a/3694410/1904043
 *
 * @author rankun203@gmail.com
 */
public class GeoTest {
    private double distance(double lat1, double lon1, double lat2, double lon2, char unit) {
        double theta = lon1 - lon2;
        double dist = Math.sin(deg2rad(lat1)) * Math.sin(deg2rad(lat2)) + Math.cos(deg2rad(lat1)) * Math.cos(deg2rad(lat2)) * Math.cos(deg2rad(theta));
        dist = Math.acos(dist);
        dist = rad2deg(dist);
        dist = dist * 60 * 1.1515;
        if (unit == 'K') {
            dist = dist * 1.609344;
        } else if (unit == 'N') {
            dist = dist * 0.8684;
        }
        return (dist);
    }

    /*:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::*/
    /*::  This function converts decimal degrees to radians             :*/
    /*:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::*/
    private double deg2rad(double deg) {
        return (deg * Math.PI / 180.0);
    }

    /*:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::*/
    /*::  This function converts radians to decimal degrees             :*/
    /*:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::*/
    private double rad2deg(double rad) {
        return (rad * 180.0 / Math.PI);
    }

    public static void main(String[] args) {
        GeoTest geo = new GeoTest();
        System.out.println(geo.distance(30.6313222, 104.053067, 30.5914415,104.0601581, 'M') + " Miles\n");
        System.out.println(geo.distance(30.6313222, 104.053067, 30.5914415,104.0601581, 'K') + " Kilometers\n");
        System.out.println(geo.distance(30.6313222, 104.053067, 30.5914415,104.0601581, 'N') + " Nautical Miles\n");
    }
}