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Apache Pekko is a toolkit for building highly concurrent, distributed, and resilient message-driven applications for Java and Scala.

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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) 2016-2022 Lightbend Inc. 
 */

package org.apache.pekko

/**
 * This type is used in generic type signatures wherever the actual value is of no importance.
 * It is a combination of Scala’s `Unit` and Java’s `Void`, which both have different issues when
 * used from the other language. An example use-case is the materialized value of a Pekko Stream for cases
 * where no result shall be returned from materialization.
 */
sealed abstract class NotUsed

case object NotUsed extends NotUsed {

  /**
   * Java API: the singleton instance
   */
  def getInstance(): NotUsed = this

  /**
   * Java API: the singleton instance
   *
   * This is equivalent to [[NotUsed.getInstance]], but can be used with static import.
   */
  def notUsed(): NotUsed = this
}