grouped

Accumulate incoming events until the specified number of elements have been accumulated and then pass the collection of elements downstream.

Simple operators

Signature

Source.groupedSource.grouped Flow.groupedFlow.grouped

Description

Accumulate incoming events until the specified number of elements have been accumulated and then pass the collection of elements downstream.

Examples

The below example demonstrates how grouped groups the accumulated elements into Seq List and maps with other operation.

Scala

Source(1 to 7).grouped(3).runForeach(println)
// Vector(1, 2, 3)
// Vector(4, 5, 6)
// Vector(7)

Source(1 to 7).grouped(3).map(_.sum).runForeach(println)
// 6   (= 1 + 2 + 3)
// 15  (= 4 + 5 + 6)
// 7   (= 7)

Java

Source.from(Arrays.asList(1, 2, 3, 4, 5, 6, 7))
    .grouped(3)
    .runForeach(System.out::println, system);
// [1, 2, 3]
// [4, 5, 6]
// [7]

Source.from(Arrays.asList(1, 2, 3, 4, 5, 6, 7))
    .grouped(3)
    .map(g -> g.stream().reduce(0, Integer::sum))
    .runForeach(System.out::println, system);
// 6   (= 1 + 2 + 3)
// 15  (= 4 + 5 + 6)
// 7   (= 7)

Reactive Streams semantics