Weird Error

private SongBook mSongBook;

private BufferedReader mReader;

private Map<String, String> mMenu;
// Lets give it songs

public  KaraokeMachine(SongBook songBook){

    mSongBook = songBook;

    mReader = new BufferedReader(new InputStreamReader(System.in));

    mMenu = new HashMap<String,String>();

    mMenu.put("add", " add  a new song to the book");
    mMenu.put("choose", "choose a song to sing");
    mMenu.put("quit", " leave it :Exit the program ");  
}

private String promptAction() throws IOException{

    System.out.printf(" There are %d songs available, your options are %n",mSongBook.getSongCount());


    for(Map.Entry<String,String> option: mMenu.entrySet()){
        System.out.printf("%s - %s %n" , option.getKey(), option.getValue());
    }

    System.out.print(" What do you want to do");

    String choice = mReader.readLine();

    return choice.trim().toLowerCase(); 
}

public void run(){

    String choice = "";

    do{
    try{
        choice = promptAction();

        switch(choice){
        case "add":
            Song song = promptNewSong();
            mSongBook.addSong(song);
            System.out.printf("%s added ! %n%n", song); // This will invoke the To String method in the Song class
            break;

        case "choose":
            String artist = PromptArtist();
            Song artistSong = promptSongForArtist(artist);
            //TODO : Add to a Song Queue
            System.out.printf(" you cose %s%n", artistSong);

        case "quit":
            System.out.println(" Thanks for the choosing the songs");
            break;

            default:
                System.out.printf("Unknown choice : '%s' . Try again %n%n%n", choice);
        }
    }
    catch(IOException ioe){
        ioe.printStackTrace();
    }
}

    while(!choice.equals("quit"));

//Code to Add The new song.

private Song promptNewSong() throws IOException{  // Return tyoe is Song bcz its returning to the class Song
    System.out.print(" Enter the Artist Name");
    String artist = mReader.readLine();
    System.out.print(" Enter the Title");
    String title = mReader.readLine();
    System.out.print(" Enter the Video URL");
    String URL = mReader.readLine();
    return new Song(artist,title,URL);
}

private String PromptArtist() throws IOException{
    System.out.println("Available artist");
    List<String> artists = new ArrayList<String>(mSongBook.getArtists());
    int index = PromptForIndex(artists);
    return artists.get(index);
}

private Song promptSongForArtist(String artist) throws IOException{
    List<Song> songs = mSongBook.getSongForArtist(artist);
    List<String> songTitles = new ArrayList<>();
    for( Song song : songs){
        songTitles.add(song.getTitile());
    }
    int index = PromptForIndex(songTitles);
    return songs.get(index);
}



private int PromptForIndex(List<String> songTitles) throws IOException{
    int count = 1;

    for(String option : songTitles){
        System.out.printf(" %d.) %s %n", count,option);
        count++;
    }

    String OptionAsString = mReader.readLine();
    int choice = Integer.parseInt(OptionAsString.trim());
    System.out.print(" Your choice");
    return count -1;


}