cannot resolve symbol f0，f1

DataStream<Tuple2<String, Long>> result = keyedEdits
        .timeWindow(Time.seconds(5))  //指定窗口的宽度为5秒
        .fold(new Tuple2<>("", 0L), new FoldFunction<WikipediaEditEvent, Tuple2<String, Long>>() {
            @Override
            public Tuple2<String, Long> fold(Tuple2<String, Long> acc, WikipediaEditEvent o) throws Exception {
                acc.f0 = o.getUser();
                acc.f1 += o.getByteDiff();
                return acc;
            }
        });