Source.cycle
Stream iterator in cycled manner.
Signature¶
Description¶
Stream iterator in cycled manner. Internally a new iterator is being created to cycle the one provided via argument meaning when the original iterator runs out of elements to process it will start all over again from the beginning of the iterator provided by the evaluation of provided parameter. If the method argument provides an empty iterator the stream will be terminated with an exception.
Examples¶
sourceSource
.cycle(() => List(1, 2, 3).iterator)
.grouped(9)
.runWith(Sink.head)
// This will produce the Seq(1, 2, 3, 1, 2, 3, 1, 2, 3)
sourcefinal Source<Integer, NotUsed> source = Source.cycle(() -> Arrays.asList(1, 2, 3).iterator());
CompletionStage<List<Integer>> result = source.grouped(9).runWith(Sink.head(), system);
List<Integer> emittedValues = result.toCompletableFuture().get();
assertThat(emittedValues, is(Arrays.asList(1, 2, 3, 1, 2, 3, 1, 2, 3)));
When iterator is empty the stream will be terminated with IllegalArgumentException
sourceval empty = Iterator.empty
Source
.cycle(() => empty)
.runWith(Sink.head)
// This will return a failed future with an `IllegalArgumentException`
sourceIterator<Integer> emptyIterator = Collections.<Integer>emptyList().iterator();
Source.cycle(() -> emptyIterator)
.runWith(Sink.head(), system)
// stream will be terminated with IllegalArgumentException
Reactive Streams semantics¶
emits the next value returned from cycled iterator
completes never
1.1.3