ConcurrentHashMap/ConcurrentMap/Map.compute

[David M. Lloyd]

On 12/14/2012 09:17 AM, Doug Lea wrote:
> On 12/14/12 10:12, David M. Lloyd wrote:
>
>> What's wrong with:
>>
>>    default V computeIfAbsent(K key, Function<? super K, ? extends V>
>> mappingFunction) {
>>        V v, newValue;
>>        if ((v = get(key)) != null) return v;
>>        newValue = mappingFunction.apply(key);
>>        return putIfAbsent(key, newValue);
>>    }
>
> putIfAbsent uses the "put" convention of returning the previous value
> or null if absent. (Arguably this was a mistake, but not one we can
> do anything about.)

Oh I see - the point I was missing is that computeIfAbsent is specified 
to return the *new* value if the mapping is replaced, instead of 
returning null as putIfAbsent does.

Now given the precedent of putIfAbsent, why change the behavior in this 
case?  Is it just because we are arguing that it was in fact a mistake?

-- 
- DML