这是类MonitoredData
:如何在Java 8中创建Map <Integer,Map <String,Integer >>类型的映射?
class MonitoredData {
public MonitoredData (DateTime startTime, DateTime endTime, String activity){
this.startTime = startTime;
this.endTime = endTime;
this.activity = activity;
}
public DateTime getStartTime(){
return this.startTime;
}
public DateTime getEndTime(){
return this.endTime;
}
public String getActivity(){
return this.activity;
}
}
我有一个返回的MonitoredData
列表的方法,我不得不生成包含日志的每一天的活动计数Map<Integer, Map<String, Integer>>
类型的数据结构。
public void activitiesPerDay(List<MonitoredData> monitoredData) {
Map <Integer, Map<String, Integer>> map = monitoredData.stream()
.collect(Collectors.groupingBy(
element -> element.getStartTime().dayOfMonth()),
Collectors.mapping(mapper, downstream)
);
}
[Java stream filter sum of values]的可能重复(https://stackoverflow.com/questions/44101297/java-stream-filter-sum-of-values) – Eugene