java Java 8中运用stream（）进行数据分组

Posted 2021-05-08

List<Map<String, Object>> textList =
  list.stream().filter(
          m->(m.get("text") != null)
  ).collect(Collectors.toList());

Map<String, Map<String, List<Map<String, Object>>>> bigMap = new HashMap<>();
List<Map<String, Object>> list = new ArrayList<>();

Map<String, List<Map<String, Object>>> map =
  list.stream().collect(
    Collectors.groupingBy(
      m->String.valueOf(m.get("type"))
    )
  );

map.forEach((k,v)->{
    Map<String, List<Map<String, Object>>> map22 = 
      v.stream().collect(
        Collectors.groupingBy(
          m->String.valueOf(m.get("date"))
        )
      );
    bigMap.put(k,map22);
});

System.out.println(bigMap);