Java 8 代码优化：使用 Stream API 获取列表数据

<p>private Collection&lt;List&lt;List<Object>&gt;&gt; getSheetDatas(final String activityId) {
final List<MidLevelDemocracyEvaluationVO> midLevelDemocracyEvaluations = getMidLevelDemocracyEvaluations(activityId);
final Map&lt;Integer, List&lt;List<Object>&gt;&gt; collect = CollectionUtils.emptyIfNull(midLevelDemocracyEvaluations)
.stream()
.collect(Collectors.groupingBy(MidLevelDemocracyEvaluationVO::getOrgSort, LinkedHashMap::new, Collectors.mapping(this::createDataObjects, Collectors.toList())));
return collect.values();
}</p>