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package cn.johnyu;

import java.util.ArrayList;
import java.util.List;
import java.util.Objects;
import java.util.stream.Stream;

import static java.util.Collections.unmodifiableList;
import static java.util.stream.Collectors.toList;


public final class Album implements Performance {
 
 private String name;
 private List<Track> tracks;
 private List<Artist> musicians;

 public Album(String name, List<Track> tracks, List<Artist> musicians) {
 Objects.requireNonNull(name);
 Objects.requireNonNull(tracks);
 Objects.requireNonNull(musicians);

 this.name = name;
 this.tracks = new ArrayList<>(tracks);
 this.musicians = new ArrayList<>(musicians);
 }

 /**
 * @return the name
 */
 public String getName() {
 return name;
 }

 /**
 * @return the tracks
 */
 public Stream<Track> getTracks() {
 return tracks.stream();
 }

 /**
 * Used in imperative code examples that need to iterate over a list
 */
 public List<Track> getTrackList() {
 return unmodifiableList(tracks);
 }

 /**
 * @return the musicians
 */
 public Stream<Artist> getMusicians() {
 return musicians.stream();
 }

 /**
 * Used in imperative code examples that need to iterate over a list
 */
 public List<Artist> getMusicianList() {
 return unmodifiableList(musicians);
 }

 public Artist getMainMusician() {
 return musicians.get(0);
 }

 public Album copy() {
 List<Track> tracks = getTracks().map(Track::copy).collect(toList());
 List<Artist> musicians = getMusicians().map(Artist::copy).collect(toList());
 return new Album(name, tracks, musicians);
 }

}