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Java

Posted by Oussama DJEDIDI
Oussama DJEDIDI
4,599 Points

java.lang.NullPointerException on the eclipe IDE

I tried run code on eclipse (Having some trouvle with internet), and I get this :

You have 7 tries left to solve --------- Exception in thread "main" java.lang.NullPointerException at Prompter.promptForGuess(Prompter.java:23) at Prompter.play(Prompter.java:13) at Hangman.main(Hangman.java:7)

Tristan Smith
Tristan Smith
3,171 Points

Hi, could you post the code you're working with? It'll help us help you. :-)

Oussama DJEDIDI
Oussama DJEDIDI
4,599 Points

This is the function for the hagman game of the Java course (I thought the question would be posted there under the video). The concerned line is : 

String guessAsString = console.readLine("Enter a Letter: ");

   public boolean promptForGuess(){
    Console console = System.console();
    boolean isHit = false;
    boolean isValideGuess = false;
    while(! isValideGuess){
    String guessAsString = console.readLine("Enter a Letter: ");
    char guess = guessAsString.charAt(0);
    try {
    isHit  = mGame.applyGuess(guess);
        isValideGuess = true;
      }catch(IllegalArgumentException iae){
        console.printf(iae.getMessage() + " Pleae try again.\n");
      }
    }
    return isHit;
  }
Tristan Smith
Tristan Smith
3,171 Points

Thanks for posting the code. Do you recall what course and video this was in? I recall going through this, but for some reason I can't find the challenge/task on the course.

Oussama DJEDIDI
Oussama DJEDIDI
4,599 Points

Sorry for my late answer (time zone difference). The code is from the Java Object Course, I believe it is the last part of it.

Tristan Smith
Tristan Smith
3,171 Points

No worries. I wasn't able to recreate the NullPointerException though, and when I put your code in the workspace for [1] it worked as it should.

If possible, could you post your entire prompter class? (Prompter.java)

Found the vids:

So the prompter class that you seem to be working with is here [1], around 7-8 minutes he adds more to it.

But here [2] at 2-3 minutes he begins to refactor the code and fixes a bug.

[1] https://teamtreehouse.com/library/java-objects/delivering-the-mvp/validation

[2] https://teamtreehouse.com/library/java-objects/delivering-the-mvp/refactoring

Oussama DJEDIDI
Oussama DJEDIDI
4,599 Points

Thanks for the answer ! The code worked for e just fine, my problem wads when I tried to run it in eclipse IDE not the workspace

1 Answer

Steve Hunter
Steve Hunter
57,712 Points

HI there,

The IDE may not come with a console object as standard. This will create a null pointer if you try to use a readLine method. Your code will work in Workspaces, which does provide a console but not in the IDE.

As a workaround, I'd suggest using a Scanner instance. I'll see if I can find a link that may help you out.

Steve.

Oussama DJEDIDI
Oussama DJEDIDI
4,599 Points

Thanks ! I see now ! When importing, it works :D

Tristan Smith
Tristan Smith
3,171 Points

Thank you, Steve! (I was testing it in workspaces, lol...).