RFR(s): 8203670: unmodifiable List iterator() implementations should not be ListIterators

[Ivan Gerasimov]

On the first place, I'd like to understand why it is bad, if 
List.of().iterator() in fact returns ListIterator?

What kind of problems it may cause?

With kind regards,
Ivan

On 6/26/18 6:50 AM, Peter Levart wrote:
>
>
> On 06/26/2018 08:11 AM, Zheka Kozlov wrote:
>> I agree with Ivan. Isn't it better to create a standalone 
>> implementation of
>> Iterator and return its instance in iterator()? Implementing of Iterator
>> for ImmutableList doesn't look like a big problem.
>
> Also, performance would be better if it was a separate class. It could 
> be a superclass of ListItr so that common logic is not duplicated.
>
> @Stable annotation on private final boolean isListIterator does not 
> help here unless the returned Iterator object is assigned to a static 
> final field and used from it. Hardly a common use case for Iterator(s) 
> I guess.
>
> Another thing about @Stable is that it never has effect on fields that 
> hold a default value. Ok, when isListIterator == false, we don't need 
> speed as we're throwing UOE anyway.
>
> The same arguments hold for other two @Stable fields in this class. I 
> don't think those three @Stable annotations have any effect on real 
> Iterator use cases.
>
> Regards, Peter
>
>>
>> 2018-06-26 6:14 GMT+07:00 Ivan Gerasimov <ivan.gerasimov at oracle.com>:
>>
>>> Hi Stuart!
>>>
>>> Out of curiosity.  What if someone does something like
>>>
>>> if (it instanceof ListIterator) {
>>>      // optimized for bidirectional access
>>> } else {
>>>      // slower algorithm
>>> }
>>>
>>> previous(), nextIndex() and previousIndex() methods are not declared 
>>> to be
>>> optional, so is it appropriate to throw 
>>> UnsupportedOperationException from
>>> them?
>>>
>>> Someone may assume that if an object can be cast to ListIterator
>>> interface, non-optional methods should not throw UOE.
>>>
>>> With kind regards,
>>>
>>> Ivan
>>>
>>>
>>>
>>> On 6/25/18 3:06 PM, Stuart Marks wrote:
>>>
>>>> Hi all,
>>>>
>>>> Please review this small changeset that ensures that calling 
>>>> iterator()
>>>> on an unmodifiable List (from List.of, et. al.) returns an instance 
>>>> that
>>>> cannot be downcast to ListIterator and used as such.
>>>>
>>>> Bug:
>>>>
>>>>      https://bugs.openjdk.java.net/browse/JDK-8203670
>>>>
>>>> Webrev:
>>>>
>>>> http://cr.openjdk.java.net/~smarks/reviews/8203670/webrev.0/
>>>>
>>>> Thanks,
>>>>
>>>> s'marks
>>>>
>>>>
>>> -- 
>>> With kind regards,
>>> Ivan Gerasimov
>>>
>>>
>
>

-- 
With kind regards,
Ivan Gerasimov