Substitute for groupingReduce ?

Brian Goetz brian.goetz at
Wed Mar 20 13:01:12 PDT 2013

More generally: all the forms of
   groupingReduce(f, stuff)
are now written as some form of
   groupingBy(f, reducing(stuff))

On 3/20/2013 3:49 PM, Michael Nascimento wrote:
> On Wed, Mar 20, 2013 at 4:36 PM, Brian Goetz <brian.goetz at> wrote:
>> I think you're missing a reduce function in that call?  I see a classifying
>> function and a merge function.
> This compiled with b76. I am migrating a code base that was running
> with a previous JDK.
> So there is no substitute that assumes the returned value is a unique
> index and throws an Exception if it is not? This is what
> Maps.uniqueIndex does:
> and what the groupingReduce variant did with the throwingMerger. I
> still didn't quite understand how to rewrite this...
> Regards,
> Michael

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