Adopt OpenJDK Lambdas Hackday at Devoxx UK

[Brian Goetz]

> We're planning on running another 3 hour hack session on Lambdas with
> about 30 attendees at Devoxx UK.

Thanks -- these have been extremely helpful so far.

> 1.) Is there a new binary drop planned in the coming week?

Can you give us the date for the hack day?

> 2.) Are there area of the API/feature set you'd like us to get attendees
> to focus on?

The aspects of the API that are most changed since the last hack day are:

  - flatMap revamped
  - reduce/collect revamped
  - many methods on Stream (e.g., into(), groupBy()) moved into collect().

For example, what was
   .into(new ArrayList<>())

is now

   .collect(toList())

and what was

   .groupBy(classifierFn)

is now

   .collect(groupingBy(classifierFn))

where toList/groupingBy are static imported from Collectors.