org.apache.pekko.stream.javadsl.MergeLatest.scala Maven / Gradle / Ivy

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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * license agreements; and to You under the Apache License, version 2.0:
 *
 *   https://www.apache.org/licenses/LICENSE-2.0
 *
 * This file is part of the Apache Pekko project, which was derived from Akka.
 */

/*
 * Copyright (C) 2018-2022 Lightbend Inc. 
 */

package org.apache.pekko.stream.javadsl

import org.apache.pekko
import pekko.stream.{ scaladsl, UniformFanInShape }
import pekko.stream.stage.GraphStage
import pekko.util.ccompat.JavaConverters._

/**
 * MergeLatest joins elements from N input streams into stream of lists of size N.
 * i-th element in list is the latest emitted element from i-th input stream.
 * MergeLatest emits list for each element emitted from some input stream,
 * but only after each stream emitted at least one element
 *
 * '''Emits when''' element is available from some input and each input emits at least one element from stream start
 *
 * '''Completes when''' all upstreams complete (eagerClose=false) or one upstream completes (eagerClose=true)
 *
 * '''Cancels when''' downstream cancels
 */
object MergeLatest {

  /**
   * Create a new `MergeLatest` with the specified number of input ports.
   *
   * @param inputPorts number of input ports
   * @param eagerComplete if true, the merge latest will complete as soon as one of its inputs completes.
   */
  def create[T](inputPorts: Int, eagerComplete: Boolean): GraphStage[UniformFanInShape[T, java.util.List[T]]] =
    new scaladsl.MergeLatest[T, java.util.List[T]](inputPorts, eagerComplete)(x => x.toList.asJava)

  /**
   * Create a new `MergeLatest` with the specified number of input ports.
   *
   * @param inputPorts number of input ports
   */
  def create[T](inputPorts: Int): GraphStage[UniformFanInShape[T, java.util.List[T]]] = create(inputPorts, false)
}