When observing a Multi, you may see duplicated items or repetitions.
Mutiny has operators to removes these duplicates.
Removing duplicates
The .transform().byDroppingDuplicates() operator removes all the duplicates.
As a result, the downstream only contains distinct items:
List<Integer> list = multi
.transform().byDroppingDuplicates()
.collectItems().asList()
.await().indefinitely();If you have a stream emitting the {1, 1, 2, 3, 4, 5, 5, 6, 1, 4, 4} items.
Applying .transform().byDroppingDuplicates() on such stream produces:
{1, 2, 3, 4, 5, 6}.
Do not use .transform().byDroppingDuplicates() on large or infinite streams.
The operator keeps a reference on all the emitted items, and so, it could lead to memory issues if the stream contains too many distinct items.
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Removing repetitions
The .transform().byDroppingRepetitions() operator removes subsequent repetition of an item:
List<Integer> list2 = multi
.transform().byDroppingRepetitions()
.collectItems().asList()
.await().indefinitely();If you have a stream emitting the {1, 1, 2, 3, 4, 5, 5, 6, 1, 4, 4} items.
Applying .transform().byDroppingRepetitions() on such stream produces:
{1, 2, 3, 4, 5, 6, 1, 4}.
Unlike .transform().byDroppingDuplicates(), you can use this operator on large or infinite streams.