summary of point lambdafication survey

[Stuart Marks]

>> * Collections.toMap(keyGen)
>>   - for each element in a Collection, generate a key, store into a Map
>>   - could be a static utility method or an extension method
> 
> This is interesting. It's sort-of halfway between two different ideas.
> 
> One take would be for it to take a value-generating lambda (a Mapper) which 
> would be run over each element in a Set. The result would be a Map object whose 
> keys are the elements from the Collection and whose values are the results from 
> the Mapper.
> 
> Another take is to generate keys from each element of a Collection; the 
> question then what to do in the case of duplicate keys. We'd want the resulting 
> Map to have multiple values for a single key. This could be expressed as a 
> (hypothetical) MultiMap, or as an ordinary Map whose values are Lists.

... which turns it into groupBy.