Collectors.groupingBy 如何对 List<Map<String,Object>>集合分组

Question

//网上对groupingBy的使用都是针对类对象的分组例子，如List<Person>、List<Student>这种。
//可是我这里有如下数据，应该怎么弄呢？

List<Map<String,Object>> list = new ArrayList<>();
Map<String,Object> map = new HashMap<>();
map.put("dicId","aaa");
map.put("dicName","钢材");
map.put("dicDes","钢材1号");
list.add(map);

map = new HashMap<>();
map.put("dicId","bbb");
map.put("dicName","钢筋");
map.put("dicDes","钢筋1号");
list.add(map);
map = new HashMap<>();
map.put("dicId","111");
map.put("dicName","钢筋");
map.put("dicDes","钢筋2号");
list.add(map);

map = new HashMap<>();
map.put("dicId","ccc");
map.put("dicName","河沙");
map.put("dicDes","河沙1号");
list.add(map);

//比如以dicId分组成为Map<String, List<Map<String,Object>>>

Answer 1

public void aaa(){
        List<Map<String,Object>> list = new ArrayList<>();
        Map<String,Object> map = new HashMap<>();
        map.put("dicId","aaa");
        map.put("dicName","钢材");
        map.put("dicDes","钢材1号");
        list.add(map);

        map = new HashMap<>();
        map.put("dicId","bbb");
        map.put("dicName","钢筋");
        map.put("dicDes","钢筋1号");
        list.add(map);
        map = new HashMap<>();
        map.put("dicId","111");
        map.put("dicName","钢筋");
        map.put("dicDes","钢筋2号");
        list.add(map);

        map = new HashMap<>();
        map.put("dicId","ccc");
        map.put("dicName","河沙");
        map.put("dicDes","河沙1号");
        list.add(map);
        Map<String, List<Map<String, Object>>> collect = list.stream().collect(Collectors.groupingBy(this::customKey));
    }

    private  String customKey(Map<String,Object> map){
        return map.get("dicId").toString();
    }