java - 将 map 转换为 map 列表

Question

我有一个要求，我想将 map 转换为 map 列表。

我尝试了以下代码，

List<Map<String, Object>> response = new ArrayList<>();
Set<Long> categories = new HashSet<>();

List<CCP> ccpList = ccpRepository.findByPIdIn(ids);
Map<Integer, List<Integer>> categoriesByProduct = ccpList.stream()
                  .collect(Collectors.groupingBy(ccp -> ccp.getPId(), Collectors.mapping(ccp-> ccp.getCId(), Collectors.toList())));
for(Entry<Integer, List<Integer>> en : categoriesByProduct.entrySet()) {
    Map<String,Object> responseObject = new HashMap<>();
    responseObject.put("pid", en.getKey());
    responseObject.put("categories",en.getValue());
    response.add(responseObject);
}

有什么方法可以修改java 8风格的以下代码:

for(Entry<Integer, List<Integer>> en : categoriesByProduct.entrySet()) {
    Map<String,Object> responseObject = new HashMap<>();
    responseObject.put("pid", en.getKey());
    responseObject.put("categories",en.getValue());
    response.add(responseObject);
}

Answer 1

将 for-loop-content 放入函数中并将其与流一起使用:

response = categoriesByProduct.entrySet()
                              .stream()
                              .map(e -> toMap(e))
                              .collect(Collectors.toList());

public static Map<String, Object> toMap(Map.Entry<Integer, List<Integer>> en) {
    Map<String,Object> responseObject = new HashMap<>();
    responseObject.put("pid", en.getKey());
    responseObject.put("categories",en.getValue());
    return responseObject;
}