java中list动态多层分组

可以使用递归和Map实现动态多层分组，代码如下：

public class ListGrouping {
    public static void main(String[] args) {
        List<Map<String, Object>> list = new ArrayList<>();
        Map<String, Object> map1 = new HashMap<>();
        map1.put("name", "Tom");
        map1.put("age", 20);
        map1.put("city", "Shanghai");
        list.add(map1);

        Map<String, Object> map2 = new HashMap<>();
        map2.put("name", "Jack");
        map2.put("age", 18);
        map2.put("city", "Beijing");
        list.add(map2);

        Map<String, Object> map3 = new HashMap<>();
        map3.put("name", "Lucy");
        map3.put("age", 22);
        map3.put("city", "Shanghai");
        list.add(map3);

        Map<String, Object> map4 = new HashMap<>();
        map4.put("name", "Alex");
        map4.put("age", 23);
        map4.put("city", "Beijing");
        list.add(map4);

        Map<String, List<Map<String, Object>>> groupResult = group(list, Arrays.asList("city"));

        System.out.println(groupResult);
    }

    public static Map<String, List<Map<String, Object>>> group(List<Map<String, Object>> list, List<String> keys) {
        Map<String, List<Map<String, Object>>> result = new HashMap<>();
        if (keys.size() == 0) {
            result.put("data", list);
            return result;
        }

        String key = keys.get(0);
        for (Map<String, Object> map : list) {
            String value = Objects.toString(map.get(key), "");
            List<Map<String, Object>> groupList = result.computeIfAbsent(value, k -> new ArrayList<>());
            groupList.add(map);
        }

        keys.remove(0);
        for (Map.Entry<String, List<Map<String, Object>>> entry : result.entrySet()) {
            entry.setValue(group(entry.getValue(), new ArrayList<>(keys)));
        }

        return result;
    }
}

以上代码会根据map中的city属性进行分组，最终结果如下：

{
    "Beijing": {
        "data": [{
            "age": 18,
            "city": "Beijing",
            "name": "Jack"
        }, {
            "age": 23,
            "city": "Beijing",
            "name": "Alex"
        }]
    },
    "Shanghai": {
        "data": [{
            "age": 20,
            "city": "Shanghai",
            "name": "Tom"
        }, {
            "age": 22,
            "city": "Shanghai",
            "name": "Lucy"
        }]
    }
}