/**
 * 计算两点之间距离
 * @param _lat1 - start纬度
 * @param _lon1 - start经度
 * @param _lat2 - end纬度
 * @param _lon2 - end经度
 * @return km(四舍五入)
 */
public static double getDistance(double _lat1,double _lon1, double _lat2,double _lon2){
 double lat1 = (Math.PI/180)*_lat1;
 double lat2 = (Math.PI/180)*_lat2;

 double lon1 = (Math.PI/180)*_lon1;
 double lon2 = (Math.PI/180)*_lon2;

 //地球半径
 double R = 6378.1;

 double d =  Math.acos(Math.sin(lat1)*Math.sin(lat2)+Math.cos(lat1)*Math.cos(lat2)*Math.cos(lon2-lon1))*R;

 return new BigDecimal(d).setScale(4,BigDecimal.ROUND_HALF_UP).doubleValue();
}

public static void main(String[] args) {
 System.out.println(getDistance(45.73990, 126.55893,45.73876, 126.55037));
}