Album.java

import java.util.ArrayList;
import java.util.LinkedList;
import java.util.List;

public class Album {

    private String name;
    private String artist;
    private ArrayList<Song> songs;

    public Album(String name, String artist) {
        this.name = name;
        this.artist = artist;
        this.songs = new ArrayList<Song>();
    }

    public boolean addSong(String title, double duration) {
        if (findSong(title) == null) {
            this.songs.add(new Song(title, duration));
            return true;
        }
        return false;
    }

    private Song findSong(String title) {
        for (Song checkedSong : this.songs) { // This is 'for each' command in Java. This is an alternative way to go
                                              // through list of entries. What it does is instead creating varianle i
                                              // and giving condition to it and i++, it actually goes through and
                                              // creates a variable called checkedSong for every entry that's actually
                                              // in our array list. It is equivalent to normal iterations of i nad do
                                              // .get(i) as we do always.
                                              // So, for every entry in 'this.songs' list, Java will create variable
                                              // checkSong of type Song.
            if (checkedSong.getTitle().equals(title)) {
                return checkedSong;
            }
        }
        return null;
    }

    public boolean addToPlaylist(int trackNumber, List<Song> playList) {
        int index = trackNumber - 1;
        if ((index >= 0) && (index < this.songs.size())) {
            playList.add(this.songs.get(index));
            return true;
        }
        System.out.println("This album does not have a track " + trackNumber);
        return false;
    }

    public boolean addToPlaylist(String title, List<Song> playList) {
        Song checkedSong = findSong(title);
        if (checkedSong != null) {
            playList.add(checkedSong);
            return true;
        }
        System.out.println("The song " + title + " is not in this album");
        return false;
    }
}