Note bulk methods in Javadocs for Collections.synchronizedXxx()

Pavel Rappo pavel.rappo at
Sat Dec 28 15:23:31 UTC 2019

If we were to add something like that to the documentation, it would probably go
under @apiNote (section "pitfalls", hehe).

As you said, the spec says just enough to infer that. So, strictly speaking,
there's no need to add that note. After all, there are infinite ways to use
these, synchronized, collections incorrectly and only one way to use them right.

Maybe we could tackle this (and similar requests in the future) by adding, once
and for all, something like:

    Consider using concurrent collections instead, such as those that can be
    found in the java.util.concurrent package.

> On 28 Dec 2019, at 09:50, Roman Leventov < at> wrote:
> I think Javadocs for Collections.synchronizedXxx() should mention not
> only "traversing it via Iterator, Spliterator or Stream" as something that
> must be synchronized externally, but also cases when a synchronized
> collection is an argument to a bulk collection method, including:
> - new ArrayList(syncList), new HashSet(syncSet),  etc.
> - List.copyOf(syncList)
> - otherColl.addAll(syncList), otherColl.removeAll(syncList),
> otherMap.putAll(syncMap).
> Though this is logically inferable, this is far from being obvious and
> apparent.

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