RFR: 8004518 & 8010122 : Default methods on Map

Ulf Zibis Ulf.Zibis at CoSoCo.de
Wed Apr 10 09:25:02 UTC 2013

Hi again,

please consider to add hash() to interface Map, as an additional performance opportunity, see:

It was rejected with:
implement a wrapper class for the "key" to customize its hash() & equals() methods

Unfortunately my earlier comment on this appears to be lost by migration to Jira, so here again:

Instantiating a wrapper object for each key contradicts the purpose of performance tuning and 
additionally increases memory footprint.


Am 08.04.2013 20:07, schrieb Mike Duigou:
> Hello all;
> This is a combined review for the new default methods on the java.util.Map interface being added for the JSR-335 lambda libraries. The reviews are being combined because they share a common unit test.
> http://cr.openjdk.java.net/~mduigou/JDK-8010122/0/webrev/
> 8004518: Add in-place operations to Map
>   forEach()
>   replaceAll()
> 8010122: Add atomic operations to Map
>   getOrDefault()
>   putIfAbsent()          *
>   remove(K, V)
>   replace(K, V)
>   replace(K, V, V)
>   compute()              *
>   merge()                *
>   computeIfAbsent()      *
>   computeIfPresent()     *
> The * operations treat null values as being absent. (ie. the same as there being no mapping for the specified key).
> The default implementations provided in Map are overridden in HashMap for performance purposes, in Hashtable for atomicity and performance purposes and in Collections for atomicity.
> Mike

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