pekko/akka-docs/src/test/java/jdocs/stream/QuickStartDocTest.java

/**
 * Copyright (C) 2016-2018 Lightbend Inc. <https://www.lightbend.com>
 */

package jdocs.stream;

//#stream-imports
import akka.stream.*;
import akka.stream.javadsl.*;
//#stream-imports

//#other-imports
import akka.Done;
import akka.NotUsed;
import akka.actor.ActorSystem;
import akka.util.ByteString;

import java.nio.file.Paths;
import java.math.BigInteger;
import java.time.Duration;
import java.util.concurrent.CompletionStage;
import java.util.concurrent.ExecutionException;

import jdocs.AbstractJavaTest;
//#other-imports

import org.junit.*;

/**
 * This class is not meant to be run as a test in the test suite, but it
 * is set up such that it can be run interactively from within an IDE.
 */
public class QuickStartDocTest extends AbstractJavaTest {
  
  @Test
  public void demonstrateSource() throws InterruptedException, ExecutionException {
    //#create-materializer
    final ActorSystem system = ActorSystem.create("QuickStart");
    final Materializer materializer = ActorMaterializer.create(system);
    //#create-materializer

    //#create-source
    final Source<Integer, NotUsed> source = Source.range(1, 100);
    //#create-source
    
    //#run-source
    source.runForeach(i -> System.out.println(i), materializer);
    //#run-source
    
    //#transform-source
    final Source<BigInteger, NotUsed> factorials =
      source
        .scan(BigInteger.ONE, (acc, next) -> acc.multiply(BigInteger.valueOf(next)));
    
    final CompletionStage<IOResult> result =
      factorials
        .map(num -> ByteString.fromString(num.toString() + "\n"))
        .runWith(FileIO.toPath(Paths.get("factorials.txt")), materializer);
    //#transform-source

    //#use-transformed-sink
    factorials.map(BigInteger::toString).runWith(lineSink("factorial2.txt"), materializer);
    //#use-transformed-sink
    
    //#add-streams
    factorials
      .zipWith(Source.range(0, 99), (num, idx) -> String.format("%d! = %s", idx, num))
      .throttle(1, Duration.ofSeconds(1), 1, ThrottleMode.shaping())
      //#add-streams
      .take(2)
      //#add-streams
      .runForeach(s -> System.out.println(s), materializer);
    //#add-streams
    
    //#run-source-and-terminate
    final CompletionStage<Done> done =
      source.runForeach(i -> System.out.println(i), materializer);

    done.thenRun(() -> system.terminate());
    //#run-source-and-terminate

    done.toCompletableFuture().get();
  }
  
  //#transform-sink
  public Sink<String, CompletionStage<IOResult>> lineSink(String filename) {
    return Flow.of(String.class)
      .map(s -> ByteString.fromString(s.toString() + "\n"))
      .toMat(FileIO.toPath(Paths.get(filename)), Keep.right());
  }
  //#transform-sink
  
}