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Java Java Objects Creating the MVP Current Progress


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.


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()); } }

2 Answers

Evan Cook ,

you need to initialize the variables "Hits" and "Misses" in the constructor like he did. After that you shouldn't anymore get the NullPointerException.


  private String answer;
  private String hits;
  private String misses;

  public Game(String answer) {
    this.answer = answer;
    this.hits = ""; // you need this
    this.misses = ""; // you need this
Moira Lawrie-Martyn
Moira Lawrie-Martyn
7,819 Points

Can you post the exact error? As it usually tells you the line where the problem is which helps you pin down the problem


Exception in thread "main" java.lang.NullPointerException at Game.getCurrentProgress(Game.java:24) at Prompter.displayProgress(Prompter.java:20) at Hangman.main(Hangman.java:8)