Error Message in Refactoring Code Problem

package com.teamtreehouse.model;


import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Queue;

public class KaraokeMachine {
    private SongBook mSongbook;
    private BufferedReader mReader;
    private Map<String, String> mMenu;
    private Queue<SongRequest> mSongRequestQueue;

    public KaraokeMachine(SongBook songbook) {
        mSongbook = songbook;
        mReader = new BufferedReader(new InputStreamReader(System.in));
        mMenu = new HashMap<String, String>();
        mSongRequestQueue = new ArrayDeque<SongRequest>();
        mMenu.put("Add", "Add a new song to the song book\n");
        mMenu.put("Play", "Play next song in queue\n");
        mMenu.put("Choose", "Choose a song to sing\n");
        mMenu.put("Quit", "Not in the mood to sing\n");
    }

    private String promptAction() throws IOException {
        System.out.printf("There are %d songs in the song book and %d in the queue. Your options are: \n", mSongbook.songCount(), mSongRequestQueue.size());
        for (Map.Entry<String, String> entry : mMenu.entrySet()) {
            System.out.format("%s-%s", entry.getKey(), entry.getValue());
        }
        System.out.println("What do you want to do ?\n");
        String choice = mReader.readLine();
        return choice.trim().toLowerCase();
    }

    public void run() {
        String choice = "add";
        do {
            try {
                choice = promptAction();
                switch (choice) {
                    case "add":
                        Song song = promptNewSong();
                        mSongbook.addSong(song);
                        System.out.printf("%s added! \n\n", song);
                        break;
                    case "choose":
                        String singerName = promptForSingerName();
                        String artist = promptArtist();
                        Song artistSong = promptSongForArtist(artist);
                        //TODO: Add song to queue
                        SongRequest songRequest = new SongRequest(singerName, artistSong);
                        mSongRequestQueue.add(songRequest);
                        if (mSongRequestQueue.contains(songRequest)) {
                            System.out.printf("\n\n %s Already Requested %s\n\n",
                                    singerName,
                                    artistSong);
                            break;
                        }
                        System.out.printf("You chose: %s\n", artistSong);
                    case "play":
                        playNext();
                        break;
                    case "quit":
                        System.out.println("Thank you for playing...");
                        break;
                    default:
                        System.out.printf("Invalid Choice %s, Try Again", choice);
                }
            } catch (IOException ioe) {
                System.out.println("Problem getting input...");
                ioe.printStackTrace();
            }
        } while (!choice.equals("quit"));

    }

    private String promptForSingerName() throws IOException {
        System.out.print("Enter the singer's name: ");
        return mReader.readLine();

    }

    private Song promptNewSong() throws IOException {
        System.out.print("Enter artist's name: \n");
        String artist = mReader.readLine();
        System.out.print("Enter song title: \n");
        String title = mReader.readLine();
        System.out.print("Enter video URL: \n");
        String videoURL = mReader.readLine();
        return new Song(artist, title, videoURL);
    }

    private String promptArtist() throws IOException {
        System.out.println("Available artists: ");
        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.getSongForArtists(artist);
        List<String> songTitles = new ArrayList<>();
        for (Song song : songs) {
            songTitles.add(song.getTitle());
        }
        System.out.printf("Available songs for %s\n", artist);
        int index = promptForIndex(songTitles);
        return songs.get(index);
    }

    private int promptForIndex(List<String> options) throws IOException {
        int counter = 1;
        for (String option : options) {
            System.out.printf("(%d.) %s\n", counter, option);
            counter++;
        }
        System.out.print("Your choice: \n");
        String optionAsString = mReader.readLine();
        int choice = Integer.parseInt(optionAsString.trim());
        return choice - 1;
    }

    public void playNext() {
        SongRequest songRequest = mSongRequestQueue.poll();
        if (songRequest == null) {
            System.out.print("Sorry there are no songs in the queue.");
        } else {
            Song song = songRequest.getMsong();
            System.out.printf("\n\nReady %s? Open %s to hear %s by %s\n",
                  songRequest.getSingerName(),
                    song.getVideoUrl(),
                    song.getTitle(),
                    song.getArtist());
        }
    }
}