```
这里有一个使用 map 做去重的，我觉得比较巧妙
datas.stream().filter(distinctByKey(s -> s.getRequestNo())).forEach(v -> {
doSomeThing(v);
});

static <T> Predicate<T> distinctByKey(Function<? super T, ?> keyExtractor) {
Map<Object, Boolean> seen = new ConcurrentHashMap<>();
return t -> seen.putIfAbsent(keyExtractor.apply(t), Boolean.TRUE) == null;
}

```