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+str #19020 reduce combinator

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This commit is contained in:
Alexander Golubev 2016-01-15 22:51:26 -05:00
parent 55425e5ef3
commit a2ab7f29e1
15 changed files with 247 additions and 37 deletions
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23
akka-docs/rst/java/code/docs/stream/javadsl/cookbook/RecipeReduceByKeyTest.java
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@ -55,8 +55,10 @@ public class RecipeReduceByKeyTest extends RecipeTest {
final Source<Pair<String, Integer>, NotUsed> counts = words
// split the words into separate streams first
.groupBy(MAXIMUM_DISTINCT_WORDS, i -> i)
//transform each element to pair with number of words in it
.map(i -> new Pair<>(i, 1))
// add counting logic to the streams
.fold(new Pair<>("", 0), (pair, elem) -> new Pair<>(elem, pair.second() + 1))
.reduce((left, right) -> new Pair<>(left.first(), left.second() + right.second()))
// get a stream of word counts
.mergeSubstreams();
//#word-count
@ -77,17 +79,13 @@ public class RecipeReduceByKeyTest extends RecipeTest {
static public <In, K, Out> Flow<In, Pair<K, Out>, NotUsed> reduceByKey(
int maximumGroupSize,
Function<In, K> groupKey,
Function<K, Out> foldZero,
Function2<Out, In, Out> fold,
Materializer mat) {
Function<In, Out> map,
Function2<Out, Out, Out> reduce) {
return Flow.<In> create()
.groupBy(maximumGroupSize, i -> i)
.fold((Pair<K, Out>) null, (pair, elem) -> {
final K key = groupKey.apply(elem);
if (pair == null) return new Pair<>(key, fold.apply(foldZero.apply(key), elem));
else return new Pair<>(key, fold.apply(pair.second(), elem));
})
.groupBy(maximumGroupSize, groupKey)
.map(i -> new Pair<>(groupKey.apply(i), map.apply(i)))
.reduce((left, right) -> new Pair<>(left.first(), reduce.apply(left.second(), right.second())))
.mergeSubstreams();
}
//#reduce-by-key-general
@ -104,9 +102,8 @@ public class RecipeReduceByKeyTest extends RecipeTest {
Source<Pair<String, Integer>, NotUsed> counts = words.via(reduceByKey(
MAXIMUM_DISTINCT_WORDS,
word -> word,
key -> 0,
(count, elem) -> count + 1,
mat));
word -> 1,
(left, right) -> left + right));
//#reduce-by-key-general2
final Future<List<Pair<String, Integer>>> f = counts.grouped(10).runWith(Sink.head(), mat);