[appB] Really basic example of starting a parallel stream.

package appB;

import ch12.JukeboxData;

import ch12.Song;

import java.util.List;

import java.util.stream.Stream;

public class ParallelStreams {

  void startAParallelStream() {

    List<Song> songs = new JukeboxData.Songs().getSongs();

    Stream<Song> songStream = songs.parallelStream();

  }

  void addAParallelOperationStream() {

    List<Song> songs = new JukeboxData.Songs().getSongs();

    Stream<Song> songStream = songs.stream()

                                   .parallel();

  }

}

// TODO: introduce duplicates for number of times played

// or: add a timesPlayed field.

public class JukeboxData {

  static class Songs {

  public static class Songs {

    public List<Song> getSongs() {

      return List.of(