就像[JEP 473: Stream Gatherers](https://openjdk.org/jeps/473),看了Gather的接口,没想到怎么实现这样的效果: ``` source.gather(a).gather(b).gather(c).collect(...) is equivalent to source.gather(a.andThen(b).andThen(c)).collect(...) ```
就像JEP 473: Stream Gatherers,看了Gather的接口,没想到怎么实现这样的效果: