Complex data types in java

Question

I have designed a data type called BingoCard which will create a random bingo card. I'm trying to make BingoCard into an array but I keep getting an error on this line: System.out.println(CurrentCard[i].toString());

I'm wondering if I've created the array correctly or am I doing something wrong? Thanks for any help in advance.

public class BingoGame {
private int[] counter;
private boolean done = false;
private int numOfCards;
private int fastestCard;

public BingoGame(int num){
numOfCards = num;
counter = new int[numOfCards];
}


public int play(){
for(int a=0;a<numOfCards;a++){
    counter[a] = 0;
}

BingoCard[] CurrentCard = new BingoCard[numOfCards];
while(!done){
    for(int i=0;i<numOfCards;i++){
        System.out.println("This is the current card:");
        System.out.println(CurrentCard[i].toString());

        int currentNum = (int)(Math.random() * 75) + 1;
        counter[i]++;
        CurrentCard[i].currentNumber(currentNum);
        CurrentCard[i].bingo();
        if(CurrentCard[i].bingo()){
            done = true;
        }
        fastestCard = i;
    }

}
return counter[fastestCard];
}

}

It's a NullPointerException

hughdini
– hughdini

2015-04-09 19:27:45 +00:00
Commented Apr 9, 2015 at 19:27 — hughdini
– hughdini, Commented Apr 9, 2015 at 19:27

Reimeus · Accepted Answer · 2015-04-09 19:31:42Z

2

Elements in an Object array are null by default. You need to instantiate the elements before attempting to invoke any methods

for (int i = 0; i < numOfCards; i++) {
    currentCard[i] = new BingoCard();
    ...
}

edited Apr 9, 2015 at 19:31

answered Apr 9, 2015 at 19:29

Reimeus

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Comments

woland · Accepted Answer · 2015-04-09 19:32:30Z

0

You created your array of bingo cards, but you have initialized no item. That's why you get that null pointer exception. ;)

answered Apr 9, 2015 at 19:32

woland

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