查看 group by 功能.

以下是任何好奇的人的示例:

Here's the example for anyone who's curious:

class DateModel implements Comparable<DateModel>{
    Integer date;
    Integer value;

    public DateModel(int date, int value){
        this.date = date; 
        this.value = value;
    }

    @Override
    public int compareTo(DateModel o) {
        return value.compareTo(o.value);
    }
}

然后，如果我们必须聚合这些模型对象的列表:

And then if we have to aggregate a list of these model objects:

// example list
List<DateModel> dateList = Arrays.asList(
  new DateModel(18,1),
  new DateModel(18,2),
  new DateModel(18,3),
  new DateModel(19,1),
  new DateModel(19,2),
  new DateModel(19,3),
  new DateModel(19,4)
);

// the following observable will give you an emission for every grouping
// for the example data above, you should get two emissions (group 18 and 19)
Observable<PriorityQueue<DateModel>> observable = 
  Observable.from(dateList)
    .groupBy(dateModel -> dateModel.date)
    .flatMap(groups -> groups.collect(PriorityQueue::new, PriorityQueue::add));

PriorityQueue 只是用于收集的结构示例.如果您从队列中弹出，您将得到 18-1、18-2、18-3 等(按照您要求的顺序).您可以使用不同的结构来仅找到最大值 &分钟

PriorityQueue was just an example of the structure used for collecting. If you pop from queue, you'll get 18-1, 18-2, 18-3 etc (in the order you asked). You can use a different structure for the purposes of only finding the max & min.