mapbox cost too much cpu

I overwrite the code like here:

public static boolean inRing(PointCustom pt, List<PointCustom> pointCustomList) {
        boolean isInside = false;
        for (int i = 0, j = pointCustomList.size() - 1; i < pointCustomList.size(); j = i++) {
            double xi = pointCustomList.get(i).getLongitude();
            double yi = pointCustomList.get(i).getLatitude();
            double xj = pointCustomList.get(j).getLongitude();
            double yj = pointCustomList.get(j).getLatitude();
            boolean intersect = (
                    (yi > pt.getLatitude()) != (yj > pt.getLatitude()))
                    && (pt.getLongitude() < (xj - xi) * (pt.getLatitude() - yi) / (yj - yi) + xi);
            if (intersect) {
                isInside = !isInside;
            }
        }
        return isInside;
    }

but i run it on the production.and find that the cpu of server cost too much ,200% CPU is consumed frequently when send 100 requests per second.
My demand is to locate in the longitude and latitude data of 100000 cities through longitude and latitude。
And the args of varible : pointCustomList storage 100000+ CityInfo object.
What problem can reduce the cost of CPU?

从提供的 inRing 方法和用于 100,000 多个城市的 PointCustom 列表开始；检查其调用路径，并在每秒 100 个请求的情况下对工作负载进行性能分析。将完成定义为保留位置结果，同时证明在可比的生产环境负载下 CPU 使用率更低。