forEach on HashMap and IdentityHashMap

Peter Levart peter.levart at
Wed Jun 12 07:45:44 UTC 2013

On 06/11/2013 11:06 PM, Mike Duigou wrote:
> On Jun 11 2013, at 09:59 , Remi Forax wrote:
>> Hi guys,
>> This mail was originality sent to lambda-lib EG but Brian ask me to also send it here to not forget.
>> We should provide an implementation of forEach for HashMap that avoid to create an Iterator,
>> HashMap is too common to not have it's dedicated implementation
> I assume you mean the forEach on the entrySet.
>> (ArrayList by example has its own implementation of forEach).
>> There is also another implementation that should have a specific implementation IdentityHashMap because
>> entrySet() creates map entries on the fly so having a specific implementation that will not allocatin entries will improve performance
>> (a lot for big identity hashmap).
> Are you suggesting adding a IdentityMap.forEach(BiConsumer) or re-using the Map.Entry passed to the consumer in entrySet().forEach(Consumer)?

That's a very good idea. Why not adding the following default method to 
Map interface:

default void forEach(BiConsumer<? super K, ? super V> sink) {
     for (Map.Entry<K, V> entry : entrySet()) {
         sink.apply(entry.getKey(), entry.getValue());

...and override it in IHM, HM/LHM, CHM with optimal implementations...

Regards, Peter

> Mike
>> cheers,
>> Rémi

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