java如何计算两个经纬度之间的距离？

/*
计算两个经纬度之间的距离  结果单位：米
 */
public static double  getDistance(String lat1Str, String lng1Str, String lat2Str, String lng2Str) {
    Double lat1 = Double.parseDouble(lat1Str);
    Double lng1 = Double.parseDouble(lng1Str);
    Double lat2 = Double.parseDouble(lat2Str);
    Double lng2 = Double.parseDouble(lng2Str);

    double radLat1 = rad(lat1);
    double radLat2 = rad(lat2);
    double a = radLat1 - radLat2;
    double b = rad(lng1) - rad(lng2);
    double s = 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)));
    s = s * EARTH_RADIUS;
    s = Math.round(s * 10000) / 10000;
    return s;
}

private static double EARTH_RADIUS = 6378137;

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