NullPointerException

I've followed what they did in the video step by step and I keep getting a NullPointerException when I run Hangman.java.

It says it's at Game.getCurrentProgress, Prompter.displayProgress, and Hangman.main.

I've looked up the null pointer exception and found that it's something along the lines of a null value being where a value should be, but I don't understand why that's happening. I've looked at this code until I'm cross eyed and can't figure out what's going wrong.

game.java:

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

public Game (String answer) { this.answer = answer;

}

public boolean applyGuess(char letter) { boolean isHit = answer.indexOf(letter) != -1; if(isHit) { hits += letter; } else { misses += letter; } return isHit; } public String getCurrentProgress() { String progress = ""; for (char letter : answer.toCharArray()) { char display = '-'; if (hits.indexOf(letter) != -1) { display = letter; } progress += display; } return progress; } }

prompter.java :

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); }

public void displayProgress() { System.out.printf("Try to solve : %s%n" , game.getCurrentProgress()); } }