Getting a java.lang.NullPointerException

public class Hangman {

  public static void main(String[] args) {
    // Your incredible code goes here...
    Game game = new Game("treehouse");

    Prompter prompter = new Prompter(game);

    boolean isHit = prompter.promptForGuess();
    if (isHit) {
      System.out.println("We got a hit!"); 
    } else {
      System.out.println("Oops missed"); 
    }
  }
}

class Game{
    private String answer;
    private String hits;
    private String misses;



    public Game(String anwer) {
      this.answer = answer;
      hits="";
      misses="";
    }

    public boolean applyGuess(char letter) {
      boolean isHit = answer.indexOf(letter) != -1;
      if (isHit) {
        hits += letter; 
      } else {
        misses += letter; 
      }
      return isHit;
    }

}

import java.util.Scanner;

class Prompter {

  private Game game;

  public Prompter(Game game) {
    this.game = game;
  }

  public boolean promptForGuess() {
    Scanner scanner = new Scanner(System.in);
    System.out.print("Enter a letter:  ");
    String guessInput = scanner.nextLine();
    char guess = guessInput.charAt(0);
    return game.applyGuess(guess);
  }



}