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Thread: null pointer exception problem

  1. #1
    Junior Member
    Join Date
    Apr 2011
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    Default null pointer exception problem

    I keep receiving a null pointer exception:
    Exception in thread "main" java.lang.NullPointerException
    at Player.evaluate(Player.java:29)
    at Player.hit(Player.java:18)
    at Game.play(Game.java:23)
    at Test.main(Test.java:6)

    I know what this error is, but the weird thing is that when I access my ArrayList it says that the size is 2 initially (which is correct). I'm really confused why Java doesn't think there's a card where I specify (error occurs at the line in Player that says cardValue=c.value();

    import java.util.ArrayList;
    public class Player {
     
    	private ArrayList<Card> hand;
    	private int runningTotal;
     
    	public Player(){
    		hand=new ArrayList<Card>();
    		runningTotal=0;
    	}
     
    	public void addCard(Card c){
    		hand.add(c);
    	}
     
    	public boolean hit(){
    		boolean isBust=false;
    		evaluate();
    		if(runningTotal>21)
    			isBust=true;
    		return isBust;
    	}
     
    	public void evaluate(){
    		int blackJValue;
    		int cardValue;
    		for(int i = (hand.size() - 1); i>=0; i--){
    			Card c = hand.get(i);
    			cardValue=c.value();
    			if(cardValue>10){
    				blackJValue=10;
    			}
    			else if(cardValue==1){
    				blackJValue=1;
    			}
    			else{
    				blackJValue=cardValue;
    			}
    			runningTotal+=blackJValue;
    		}
    	}
     
    	public int getScore(){
    		return runningTotal;
    	}
     
    	public int getHandLength(){
    		return hand.size();
    	}
     
    }
    public class Deck {
     
    	private Card[] deck;
    	private int usedCards;
     
    	public Deck(){
    			deck = new Card[52];
    			int cardCount=0;
    			for(int suit=0; suit>=3; suit++){
    				for(int value=1;value>=13;value++){
    					deck[cardCount]=new Card(suit, value);
    					cardCount++;
    				}
    			}
    	}
     
    	public void shuffle(){
    		for(int i=51; i>0; i--){
    			int random = (int)(Math.random()*52);
    			Card temp = deck[i];
    			deck[i]=deck[random];
    			deck[random]= temp;
    		}
    		usedCards=0;		
    	}
     
    	public int getCardsUsed(){
    		return usedCards;
    	}
     
     
    	public Card dealCard(){
    		usedCards++;		
    		return deck[usedCards-1];
    	}
    	public String toString(int i){
    		Card c = deck[i];
    		return c.toString();
    	}
    }
    import java.util.Scanner;
    public class Game {
     
    Scanner blackJ = new Scanner(System.in);
    private Deck d;
    private Dealer p1;
    private Player p2;
     
    public Game(){
    	d=new Deck();
    	p1=new Dealer();
    	p2=new Player();
    }
     
    public void play(){
    	d.shuffle();
    	p1.addCard(d.dealCard());
    	p1.addCard(d.dealCard());
    	p2.addCard(d.dealCard());
    	p2.addCard(d.dealCard());
    	System.out.println(p2.getHandLength());
    	int choice;
    	while(p2.hit())
    		choice=0;
    		System.out.println("Hit? 1 - yes, 0 - no: ");
    		choice=blackJ.nextInt();
    		if(choice==1)
    			p2.addCard(d.dealCard());
    	while(p1.hit()){
    		while(p1.getScore()<17)
    			p1.addCard(d.dealCard());
    	}
    	getScore();
    }
     
    private void getScore(){
    	int scorep1 = p1.getScore();
    	int scorep2 = p2.getScore();
    	if(scorep1>scorep2 && scorep1<=21)
    		System.out.println("You win this round.");
    	else if(scorep1==scorep2 && scorep1<=21)
    		System.out.println("It's a push.");
    	else if(scorep1<scorep2 && scorep2<=21)
    		System.out.println("You lose this round.");
    	else if(scorep1>21)
    		System.out.println("you busted. ");
    	else
    		System.out.println("Dealer busted. ");
    }
     
    }


  2. #2
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    Default Re: null pointer exception problem

    Sorry, found it: problem was booleans in constructing deck.

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