如何在图表中可视化具有多个级别的java复杂集合对象

Question

如何在图表中可视化 java 集合对象？比起文字和书籍，我更擅长处理图片和视频。

如果地图的键为字符串，列表为值。
上面的列表还有另一个自定义对象列表。
自定义对象有另一个列表。

这些类型的场景经常出现在实际项目中。
如何描绘和想象这些类型的场景以推进编码？

Answer 1

想象一下这样的例子。您的每个朋友都有他或她访问过的国家/地区的列表。

键是String名称，值是List<Country>。

Map countriesVisited = new HashMap<String, List<Country>>();

每个国家/地区都有许多您的朋友去过的城市。例如，李在乌克兰访问了基辅、敖德萨和利沃夫。在基辅，他参观了 3 个名胜古迹：

代码如下。试试看它是如何工作的：

public class Travellers {
    
    public static void main(String[] args) {
        Country countryUkraine = new Country("Ukraine");
        
        Map countriesVisited = new HashMap<String, List<Country>>();
        countriesVisited.put("George", Arrays.asList(
                new Country("Japan"), new Country("Brazil"), new Country("Poland"), 
                new Country("Croatia"), new Country("Nigeria"), new Country("Laos"), 
                new Country("Germany")
        ));
        countriesVisited.put("Li", Arrays.asList(
                new Country("Argentina"), countryUkraine, new Country("Italy"), 
                new Country("Great Britain"), new Country("Nepal")
        ));
        countriesVisited.put("Keith", Arrays.asList(
                new Country("Egypt"), new Country("Greece"), new Country("Lebanon"), 
                new Country("Marocco"), new Country("Saudi Arabia"), new Country("Kuwait")
        ));
        countriesVisited.put("Jenny", Arrays.asList(
                new Country("Norway"), new Country("Canada"), new Country("Russia"), 
                new Country("Antarctica"), new Country("Finland")
        ));
        
        City cityKyiv = new City("Kyiv");
        countryUkraine.setCities(Arrays.asList(
                cityKyiv, new City("Odesa"), new City("Lviv")));
        Place placeKyiv1 = new Place("Lavra");
        Place placeKyiv2 = new Place("St Andrew’s Church");
        Place placeKyiv3 = new Place("Museum of Folk Architecture");
        cityKyiv.setPlaces(Arrays.asList(placeKyiv1, placeKyiv2, placeKyiv3));
        
        System.out.println("Countries visited by George: " + countriesVisited.get("George"));
        System.out.println("Countries visited by Li: " + countriesVisited.get("Li"));
        System.out.println("Countries visited by Keith: " + countriesVisited.get("Keith"));
        System.out.println("Countries visited by Jenny: " + countriesVisited.get("Jenny"));
        System.out.println();
        System.out.println("Cities visited by Li in Ukraine: " + countryUkraine.getCities());
        System.out.println();
        System.out.println("Places visited by Li in Kyiv: " + cityKyiv.getPlaces());
    }
}

class Country {
    String name;
    List<City> cities;

    Country(String name) {
        this.name = name;
    }
    
    void setCities(List<City> cities) {
        this.cities = cities;
    }
    
    List<City> getCities() {
        return cities;
    }
    
    @Override public String toString() {
        return name;
    }
}

class City {
    String name;
    List<Place> places;
    
    City(String name) {
        this.name = name;
    }
    
    void setPlaces(List<Place> places) {
        this.places = places;
    }
    
    List<Place> getPlaces() {
        return places;
    }
    
    @Override public String toString() {
        return name;
    }
}

class Place {
    String name;
    int rating;
    float latitude;
    float longitude;
    Image img;
    
    Place(String name) {
        this.name = name;
    }
    
    @Override public String toString() {
        return name;
    }
}