Java Programming

Hey all, I am writing a poker game, with not much luck!

As far as hand evaluating goes, I decided not to use some sort of numerical evaluating system to calculate the higher values of hands. Instead, I created a different class for all of the hand ( FourOfAKind, TwoPair, etc etc ).

Each of them extends another class called Hand.

So anyways, I get this NPE sometimes and I cant exactly pinpoint the cause of it.

Exception in thread "AWT-EventQueue-0" 
java.lang.NullPointerException
        at OnePair.compareTo(OnePair.java:90)
        at Hand.compareTo(Hand.java:54)
        at HandEvaluator.determineHand(HandEvaluator.java:97)
        at HandEvaluator.evaluate(HandEvaluator.java:43)
        at HandEvaluator.<init>(HandEvaluator.java:27)
        at Player.getBestHand(Player.java:50)
        at Dealer.updateHands(Dealer.java:96)
        at Dealer.doAction(Dealer.java:70)
        at GameManager.playHand(GameManager.java:42)

Since there is wayy to much code to post it all, I'll post a few pieces from the lines refferred to in the output above.

//at OnePair.compareTo(OnePair.java:90)
 public int compareTo( OnePair op )
 {
        Value thisPair = getPairValue();
        Value opPair = op.getPairValue();
        
        if( thisPair.compareTo( opPair ) > 0 )
            return 1;
        else if( thisPair.compareTo( opPair) < 0 )
            return -1;
        else // check the high card
}

The error is occuring at

 if( thisPair.compareTo( opPair ) > 0 )

This implies that thisPair == null, which implies that getPairValue() has something wrong.

public Value getPairValue ()
{
        for( Card c: hand )
        {
            Value pair = c.getValue ();
            int count = 0;
            // Compare the current cards value to the rest of the hand
            // to check for another card of the same value.
            for( Card d: hand ) 
                if( d.getValue ().equals (pair))
                    count ++;
            if( count == 2 ) return pair;
        }
        return null;
}

In order for getPairValue() to return null, it implies that none of the cards in the 'hand' which is an ArrayList< Card > of length (5) always form a pair.

So, this implies that this Hand should not be of the type OnePair at all!.. which implies that there is something wrong elsewhere in determining if a hand is a OnePair, TwoPair, etc.

So... this leads to where I determine if a given set of cards contains one pair, in the HandEvaluator class..

private boolean isOnePair ( ArrayList< Card > cards )
{
      for( Card c: cards )
      {
          Value pair = c.getValue ();
          int count = 0;
          for( Card d: cards )
              if( d.getValue ().equals ( pair )) count ++;
          if( count == 2 )  return true;
      }
      return false;
    }

So, when determining what kind of hand a particular group of cards forms, i use this isOnePair() method. If it is a pair, then it should be safe to construct a new OnePair object.

if( isRoyalFlush( cards ) )
....
else if ( is TwoPair( cards ) )
...
else if( isOnePair ( cards ))
            return new OnePair (cards);

Back to the original problem, I cant figure out why getPairValue() in the OnePair class is getting to the 'return null' line. Since I already checked whether the hand had a pair before even constructing the OnePair object, this return null case should never occur.

Oh yea. Value is just an enum

public enum Value
{
    ACE, TWO, THREE, FOUR, FIVE, SIX, SEVEN, EIGHT, NINE, TEN, JACK, QUEEN, KING;
}

Any ideas?