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

/*
 * Copyright (C) 2016-2019 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 {
    final ActorSystem system = ActorSystem.create("QuickStart");

    // #create-source
    final Source<Integer, NotUsed> source = Source.range(1, 100);
    // #create-source

    // #run-source
    source.runForeach(i -> System.out.println(i), system);
    // #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")), system);
    // #transform-source

    // #use-transformed-sink
    factorials.map(BigInteger::toString).runWith(lineSink("factorial2.txt"), system);
    // #use-transformed-sink

    // #add-streams
    factorials
        .zipWith(Source.range(0, 99), (num, idx) -> String.format("%d! = %s", idx, num))
        .throttle(1, Duration.ofSeconds(1))
        // #add-streams
        .take(2)
        // #add-streams
        .runForeach(s -> System.out.println(s), system);
    // #add-streams

    // #run-source-and-terminate
    final CompletionStage<Done> done = source.runForeach(i -> System.out.println(i), system);

    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

}