Collections.emptyList().spliterator() is not ORDERED

Paul Sandoz paul.sandoz at
Mon Sep 14 10:24:35 UTC 2015

On 7 Sep 2015, at 15:23, Paul Sandoz <Paul.Sandoz at> wrote:
>> By the way, probably it's reasonable then for Arrays.asList to check
>> the array length like:
>>   public static <T> List<T> asList(T... a) {
>>       if(a.length == 0)
>>         return Collections.emptyList();
>>       return new ArrayList<>(a);
>>   }
>> This would make Arrays.asList() (without arguments) and
>> Collections.emptyList() perfectly consistent (now their spliterators
>> report different characteristics) and reduce the number of heap
>> objects. Probably there are some caveats I'm not aware of. Sorry if it
>> was already discussed.
> This has not been discussed, it’s an edge case micro-optimisation but seems reasonable.

There is a reason not to do this. At the moment Arrays.asList specifies no constraints on the identity of the returned List. Adding the micro-optimisation will change that. It’s an edge case and a questionable use-case too, but considering that i would conservatively leave things as they are.


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