Optimize (Linked-)HashMap lookup when backing array is null

[Roger Riggs]

Hi,

Right, its only in the case of removing the node because the new value 
was null.
Besides being infrequent, that should not be a problem.

Thanks, Roger


On 5/19/20 3:56 PM, Christoph Dreis wrote:
> Hi Roger,
>
>> How does the performance degrade when the computation of the hash
>> is non-trivial. For example, with an array as a key or an object with
>> fields that are objects?
>> The original code made a point of computing the hash only once.
> HashMap.get() and HashMap.containsKey() etc. would still calculate it only once.
> Only computeIfPresent would degrade. Did you mean that?
>
> Cheers,
> Christoph
>
> On 5/19/20 3:21 PM, Claes Redestad wrote:
>>> Thanks for producing the simpler variant and getting some comparative
>>> runs done.
>>>
>>> On 2020-05-19 19:50, Christoph Dreis wrote:
>>>> I would probably go for the first version although it is a bit more
>>>> complicated and has the computeIfPresent caveat, because it doesn't
>>>> slow down the common Map.get() case when the map is actually filled.
>>> It is a bit of step up in complexity, but getting the win without adding
>>> a branch to Map.get() _is_ a nice property.
>>>
>>>> Let me know what you think.
>>> If core libs maintainers are fine with the added complexity of your
>>> original patch, I think it looks ok.
>>>
>>> /Claes
>
>