Java 8 collector for Guava immutable collections

guavajavajava-stream

I really like Java 8 streams and Guava's immutable collections, but I can't figure out how to use the two together.

For example, how do I implement a Java 8 Collector that gathers stream results into an ImmutableMultimap?

Bonus points: I'd like to be able to provide key/value mappers, similar to how Collectors.toMap() works.

Best Solution

Since version 21, you can

.collect(ImmutableSet.toImmutableSet())
.collect(ImmutableMap.toImmutableMap())
.collect(Maps.toImmutableEnumMap())
.collect(Sets.toImmutableEnumSet())
.collect(Tables.toTable())
.collect(ImmutableList.toImmutableList())
.collect(Multimaps.toMultimap(...))