package com.doumee.core.utils;
public class DistanceCalculator {
    private static final double EARTH_RADIUS = 6371.0; // 地球半径（单位：公里）

    public static void main(String[] args) {
        //118.363428,31.326485
        //118.363312,31.326638
        System.out.println(calculateDistance(39.326638d,116.363312d,31.326606,118.363272));
    }
    public static long calculateDistance(double lat1, double lon1, double lat2, double lon2) {
        double dLat = Math.toRadians(lat2 - lat1);
        double dLon = Math.toRadians(lon2 - lon1);

        double a = Math.sin(dLat / 2) * Math.sin(dLat / 2) +
                Math.cos(Math.toRadians(lat1)) * Math.cos(Math.toRadians(lat2)) *
                        Math.sin(dLon / 2) * Math.sin(dLon / 2);
        double c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));

        return  (long) (EARTH_RADIUS * c * 1000);
    }
}