java計算兩地距離(公里)

//目標經度，目標緯度，自己經度，自己緯度

public static double getDistance(double lon1, double lat1, double lon2, double lat2) {

double radLat1 = rad(lat1);
double radLat2 = rad(lat2);

double a = radLat1 - radLat2;
double b = rad(lon1) - rad(lon2);

double c = 2 * Math.asin(Math.sqrt(
Math.pow(Math.sin(a / 2), 2) + Math.cos(radLat1) * Math.cos(radLat2) * Math.pow(Math.sin(b / 2), 2)));

c = c * 6378.137;// 6378.137赤道半徑

return Math.round(c * 10000d) / 10000d;

}

private static double rad(double d) {
return d * Math.PI / 180.0;
}