DataStream<Tuple2<String, Long>> result = mappedStream
                .timeWindow(Time.seconds(30))
                .fold(new Tuple2<>("", 0L), new FoldFunction<Pojo, Tuple2<String, Long>>() {
                    @Override
                    public Tuple2<String, Long> fold(Tuple2<String, Long> acc, Pojo event) {
                        acc.f0 = event.getEt();
                        acc.f1 += 1;
                        return acc;
                    }
                });

我有一个数据流，其中有每个keyedstream的计数。我现在只想根据计数筛选前“k”个项目。