java8中的Collectors.groupingBy用法

java8二次收集备忘：

Map mapAnchor = anchors.stream().collect(Collectors.groupingBy(LiveAnchorInfo::getRoomId, Collectors.mapping(LiveAnchorInfo::getName, Collectors.joining(","))));

原文：

https://blog.csdn.net/u014231523/article/details/102535902