New methods in java.util.Map

[Brian Goetz]

I'll just add: corelibs-dev is the right place for this discussion, not 
amber-dev.

On 10/16/2025 11:05 PM, Ethan McCue wrote:
> I don't have anything intelligent to add, but I assume either
>
> * It's a good / okay idea, not high priority
> * putIfAbsent and computeIfAbsent are seen to be enough for lazy 
> operations
> * Something much more subtle and/or annoying about how it will affect 
> the universe of map implementations.
>
> Either way, just so there is something concrete to talk about:
>
> import module java.base;
>
> public final class Maps {
>     private Maps() {
>     }
>
>     private static final Object DEFAULT = new Object();
>
>     @SuppressWarnings({"unchecked","rawtypes"})
>     public static <K, V> V getOrCompute(
>             Map<K, ? extends V> m,
>             Object key,
>             Function<? super K, ? extends V> compute
>     ) {
>         Object value = ((Map) m).getOrDefault(key, DEFAULT);
>         if (value == DEFAULT) {
>             return compute.apply((K) key);
>         }
>         else {
>             return (V) value;
>         }
>     }
> }
>
> (Note the three needed casts - this might be difficult for the same 
> reason Map#gettakes an Objectand not a K)
>
> On Thu, Oct 16, 2025 at 7:20 PM Chris Bouchard 
> <chris at upliftinglemma.net> wrote:
>
>     Alberto,
>
>     I believe your getOrPut methods already exist as putIfAbsent and
>     computeIfAbsent, unless I'm missing a subtle difference.
>
>     On Thu, Oct 16, 2025, 14:20 Alberto Otero Rodríguez
>     <alber84ou at gmail.com> wrote:
>
>         Also, other two new methods might be interesting if you want
>         to get a value from a map, but if the key doesn't exist you
>         want to insert that value in the map and return it:
>
>         default V getOrPut(Object key, V defaultValue)
>
>         default V getOrPut(Object key,  Function<? super K, ? extends
>         V> defaultValueFunction)
>
>
>     Chris
>
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