#arrayList parallelStream 问题

List<Long> userIdList = new ArrayList<>();
groupHashMap.values().parallelStream().forEach(u -> {
    userIdList.add(u.getSponsor_user_id());
});
这里有bug.parallelStream并发多线程扩容问题

1. 去掉parallelStream
2. 初始化arraylist size

https://my.oschina.net/7001/blog/1475500