计算java中坐标之间的距离

Question

我有一个getNearestSuperMarket方法，可以在靠近我所在位置的最近的超级市场列表中返回。我从calculateDistance方法得到的结果是错误的。你知道哪种方法最有效吗？

limit=9000000 //in meters

public List<Market> getNearestMarkets(String lat1, String lng1) throws Exception{ 
    flat1 = Float.parseFloat(lat1);
    flng1 = Float.parseFloat(lng1);         
    list_markets2=getAllMarkets(); //returns all the markets from the database

    for ( Market ma: list_markets2){

        x1=ma.getLatitude_market();
        y1=Float.parseFloat(x1);

        x2=ma.getLongtitude_market();
        y2=Float.parseFloat(x2);

        dist=calculateDistance(flat1,flng1,y1,y2);
        try{
            if ( dist< limit ){
                ma.setDistance(dist);
                list_nearest_markets.add(ma);
            }
        }
        catch (NumberFormatException ex){
            throw new Exception("somethings happened"+ex.getMessage());
        }
        catch (Exception e0){
            errorMessages ="error: "+e0.getMessage();
            throw new Exception(e0.getMessage());
        }
    }

    return list_nearest_markets;

}//end of method


public float calculateDistance(float flat1, float flng1, float flat2, float flng2) throws Exception{

    try{

        double earthRadius = 6371000; //meters
        double dLat = Math.toRadians(flat2-flat1);
        double dLng = Math.toRadians(flng2-flng1);
        double a = Math.sin(dLat/2) * Math.sin(dLat/2) +
        Math.cos(Math.toRadians(flat1)) * Math.cos(Math.toRadians(flat2)) *
        Math.sin(dLng/2) * Math.sin(dLng/2);
        double c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a));
        float dist = (float) (earthRadius * c);
        return dist; 

    }catch(Exception e10){
        throw new Exception("error"+e10.getMessage());
    }
}//end of method