Null Pointer Exception with if statement with Array

Question

I keep getting a null pointer exception at the line surrounded by stars. How can I fix this? I don't understand why it's happening because I filled currentGuessArray with false. (I didn't include all of my code, just the parts that have to do with currentGuessArray.)

public static boolean [] currentGuessArray;


public void initGuess() { 
   // creates a new Array for the currentGuessArray variable 
   boolean [] currentGuessArray = new boolean[20];
   // initialize all slots to false
   Arrays.fill(currentGuessArray, false);
}

public String getCurrentGuessArray() { 
   // the returned String has "_ " for unrevealed letters
   // “walk over” the currentWord and currentGuessArray Arrays and create the String
   if ( !currentWord.equals("Shrek") && !currentWord.equals("Dobby") ) {
       int j = 1;
       while ( (!currentWord.substring(j, j).equals(" ")) && (j < currentWord.length()) ) {
          j++;
          spaceSpot = j;
       }
   }
   int k = 0;
   String displayString = "";
   while ( k < currentWord.length() ) {
      if ( k == spaceSpot ) {
         displayString = displayString + "   ";
      }
      **else if ( currentGuessArray[k] == true ) {**
         displayString = displayString + currentWord.substring(k, k);
      }
      else {
         displayString = displayString + "_ ";
      }
      k++;
   }
   return displayString;        
}

Any specific reason why currentGuessArray array is static? — Pshemo
– Pshemo, Commented Jun 20, 2015 at 13:33

Reimeus · Accepted Answer · 2015-06-20 13:47:51Z

4

Assuming initGuess is being called, you're shadowing currentGuessArray. Replace

boolean [] currentGuessArray = new boolean[20];

with

currentGuessArray = new boolean[20];

edited Jun 20, 2015 at 13:47

answered Jun 20, 2015 at 13:31

Reimeus

160k16 gold badges225 silver badges282 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Reisclef · Accepted Answer · 2015-06-20 13:40:34Z

0

You've defined a local variable with the same name as the class variable.

Therefore, the local variable is being declared, filled with false, and then it's garbage collected at the end of the method.

When you're referencing currentGuessArray (as a class variable I suppose somewhere in client code), it has never been set to a reference of anything, therefore you get the null pointer exception. Try the below:

public static boolean [] currentGuessArray;


public void initGuess() { 
   // creates a new Array for the currentGuessArray variable 
   currentGuessArray = new boolean[20];                       //Reisclef changed this line
   // initialize all slots to false
   Arrays.fill(currentGuessArray, false);
}

edited Jun 20, 2015 at 13:40

answered Jun 20, 2015 at 13:32

Reisclef

2,1561 gold badge23 silver badges26 bronze badges

Collectives™ on Stack Overflow

Null Pointer Exception with if statement with Array

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related