Welcome to the Treehouse Community

The Treehouse Community is a meeting place for developers, designers, and programmers of all backgrounds and skill levels to get support. Collaborate here on code errors or bugs that you need feedback on, or asking for an extra set of eyes on your latest project. Join thousands of Treehouse students and alumni in the community today. (Note: Only Treehouse students can comment or ask questions, but non-students are welcome to browse our conversations.)

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and a supportive community. Start your free trial today.


Arshan Khanifar
Arshan Khanifar
11,497 Points

what's NullPointerException error?

I'm making the hangman game myself and I'm following along with the video, but I don't know where my problem is :

this is my code:

public class Game { private String mAnswer; private String mHits; private String mMisses;

public Game(String answer) { answer = mAnswer; mHits = ""; mMisses = "";


public boolean applyGuess(char letter) {

boolean isHit = mAnswer.indexOf(letter) >=0 ; 
if (isHit) {
  mHits += letter; 
}else {
  mMisses += letter;

return isHit; 



and I open up the repl and load the game. and I make the game class, but when I'm using the method applyGuess i get this error:


2 Answers

Nicolas Hampton
Nicolas Hampton
44,625 Points

answer = mAnswer; should be mAnswer = answer;

Try that.