public class Main {
    public static void main(String[] args) {
        City bj = new City();//创建一个实例instance，并且通过bj指向它
        bj.name = "Beijing";
        bj.latitude = 39.903;
        bj.longitude = 116.401;
        System.out.println(bj.name);
        System.out.println("location: " + bj.latitude + ", " + bj.longitude);
    }
}

class City {//定义一个类class，包含以下三个字段
    public String name;
    public Double latitude;
    public Double longitude;
}