这段代码并不接近完成，为了通过编写它来测试它我必须通过这些错误。所有类都编译但是当我运行它时会出现以下错误：
Exception in thread "main" java.lang.NullPointerException
at Deck.<init>(Deck.java:41).
at Dealer.<init>(Dealer.java:25).
at Poker.main(Poker.java:16).
以下是我目前的代码。发生错误时出现的粗体
public class Dealer
{
private Deck deck;
private Player[] players;
public static final int NUMBER_OF_PLAYERS = 2;
/**
* Default constructor - creates and populates the Player array and the
* Deck object.
*/
public Dealer()
{
players = new Player[ NUMBER_OF_PLAYERS ];
**deck = new Deck();**
// populate the array of players
} // constructor
/**
* Outermost level of abstraction for the poker game
*/
public void play()
{
System.out.println("Welcome to Poker!");
} // method play
}
public class Poker
{
public static void main( String[] args )
{
Dealer dealer;
**dealer = new Dealer();**
dealer.play();
}
}
public class Card
{
private int face;
private int suit;
public static final int CLUBS = 100;
public static final int DIAMONDS = 200;
public static final int HEARTS = 300;
public static final int SPADES = 400;
/**
* Default Value Constructor - for stubs only!!!
*/
public Card()
{
// do nothing in it
} // default value constructur
/**
* Explicit Value Constructor
*/
public Card( int cardFace, int cardSuit )
{
face = cardFace;
suit = cardSuit;
} // constructor
/**
* Returns the face of the card as a String
*
* @return the face of the card
*/
public String getFace()
{
String returnVal;
switch ( face )
{
case 11: returnVal = "Jack"; break;
case 12: returnVal = "Queen"; break;
case 13: returnVal = "King"; break;
case 14: returnVal = "Ace"; break;
default: returnVal = "" + face;
} // end switch
return returnVal;
} // method getFace
/**
* Return the numeric face value
*
* @return the numeric face value
*/
public int getFaceValue()
{
return face;
} // method getFaceValue
/**
* Returns the suit of the card as a String
*
* @return the suit of the card as a String
*/
public String getSuit()
{
String returnVal;
returnVal = "Error";
switch ( suit )
{
case CLUBS: returnVal = "Clubs"; break;
case DIAMONDS:returnVal = "Diamonds"; break;
case HEARTS: returnVal = "Hearts"; break;
case SPADES: returnVal = "Spades";
} // end switch
return returnVal;
} // method getSuit
/**
* Return the numeric suite value
*
* @return the numeric suite value
*/
public int getSuitValue()
{
return suit;
} // method getSuitValue()
/**
* Returns true of the two cards have the same value and the same suit.
* Use this to test for validity (this should never happen!!!).
*
* @param the card to compare with this one
* @return true if the 2 cards have the same face value and suit
*/
public boolean equals( Card other )
{
return getFaceValue() == other.getFaceValue() &&
getSuitValue() == other.getSuitValue();
} // method equals
/**
* Return the card as a String
*
* @return the String value for the card
*/
public String toString()
{
return getFace() + " of " + getSuit();
} // method toString
}
public class Deck
{
private int pointer = 0; // indicates the current position in the deck.
// This should begin with 0 (the first call)
// and increment every time a card is dealt.
private Card deck[];
private Card tempDeck[];
private Card Card[];
public static final int CARDS_IN_DECK = 52;
/**
* Instantiate an array of Cards and populate the array with 52 Card
* objects. The face values of the cards should be between 2 - 14.
* Values 2 - 10 represent the number cards. Values 11 - 14 represent
* Jack, Queen, King, and Ace, respectively. The suits should be as
* follows: 100 = Clubs, 200 = Diamonds, 300 = Hearts, and 400 = Spades.
* See the Card class for more information.
*
* You should both shuffle and cut the cards before this method
* concludes.
*/
public Deck()
{
int i = 0;
for(int a = 1; a <= 4; a++)
{
for(int b = 2; b <=14; b++)
{
**deck[i] = new Card(a,b);**
if(deck[i] == null)
{
System.out.println("Shouldnt get here");
}
i++;
}
}
shuffle();
cut();
} // default constructor
/**
* Cut the deck. Choose a point in the deck (this can be either random
* or fixed) and re-arrange the cards. For example, if you choose to
* cut at position 26, then the 27th - 52nd cards will be placed in the
* 1st - 26th positions. The 1st - 26th cards will be placed in the
* 27th - 52nd positions.
*/
public void cut()
{
int cut = 26;
int a = 0;
int b = 0;
for(int i = 0 ; i<cut; i++)
{
tempDeck[i] = new Card(a,b);
tempDeck[i] = deck[i+26];
tempDeck[i+26] = deck[i];
}
deck = tempDeck;
}
// method cut
/**
* Deal 5 cards from the deck. Deal out the next 5 cards and return
* these in an array. You will need to maintain a pointer that lets
* you know where you are in the deck. You should make sure also
* to reshuffle and cut the deck and start over if there are not enough
* cards left to deal a hand.
*
* @return an array of 5 cards
*/
public Card[] deal(int[] args)
{
int i = 0;
int a = 0;
int b = 0;
Card[i] = new Card(a,b);
for(i = 0; i < 5; i++)
{
Card[pointer] = deck[pointer];
pointer++;
}
return Card;
// this is a stub only - replace this!!!!
} // method deal
/**
* Get a card from the deck
*
* @param the position of the card you are retrieving
* @return the card object
*/
public Card getCard( int card )
{
Card oneCard = deck[pointer];
deck[pointer] = null;
pointer +=1;
return oneCard; // this is a stub only - replace this!!!
} // method getCard
/**
* Shuffle the deck. Randomly re-arrange the cards in the deck. There
* are plenty of algorithms for doing this - check out Google!!!
*/
public void shuffle()
{
int i, j, k;
int n = 15;
for ( k = 0; k < n; k++ )
{
i = (int) ( CARDS_IN_DECK * Math.random() ); // Pick 2 random cards
j = (int) ( CARDS_IN_DECK * Math.random() ); // in the deck
Card tmp = deck[i];
deck[i] = deck[j];
deck[j] = tmp;
}
pointer = 0; // Reset current card to deal
} // end shuffle
}
public class Player
{
private int bet;
private int chips;
int totalChips;
private Hand hand;
private String name;
public static final int START_CHIPS = 100;
public static final int WINNING_CHIPS = 200;
Scanner scan = new Scanner(System.in);
/**
* Sets the player's name and the starting number of chips.
*
* @param the player's name
*/
public Player( String n )
{
System.out.println("Enter name: ");
name = scan.nextLine();
totalChips = START_CHIPS;
} // constructor
/**
* Sets the amount of the bet and decreases the number of chips that
* the player has by the number of chips bet. Do not allow bets if
* there are not enough chips left.
*
* @param the number of chips bet
* @return true if the bet was successful (there were enough chips)
*/
public boolean bet( int bet )
{
int chipsAB;
boolean canBet;
//Get Bet
getBet();
//Se if player has enough chips for bet
if(chips >= bet)
{
chipsAB = chips - bet;
canBet = true;
}
else
{
System.out.println("You do not have enough chips.");
canBet = false;
}
return canBet; // this is a stub only - replace this!!!!
} // method bet
/**
* Return the number of chips bet
*
* @return the number of chips bet
*/ //DONE
public int getBet()
{
int bet;
System.out.println("Enter bet: ");
bet = scan.nextInt();
while (bet < 1 || bet > getChips())
{
System.out.println("Error. Re-enter bet: ");
bet = scan.nextInt();
}
return bet; // this is a stub only - replace this!!!!
} // method getBet
/**
* Return the number of chips currently held
*
* @return the number of chips held
*/
public int getChips()
{
int totalChips = 0;
totalChips = winHand();
return totalChips; // this is a stub only - replace this!!!!
} // method getChips
/**
* Return the player's hand
*
* @return the player's hand object
*/
public Hand getHand()
{
return new Hand(); // this is a stub only - replace this!!!!
} // method getHand
/**
* Return the player's name
*
* @return the player's name
*/
public String getName()
{
return name; // this is a stub only - replace this!!!!
} // method getName
/**
* Indicates whether this player has won
*
* @return true if the player has more than the number of winning points
*/
public boolean hasWon()
{
boolean won = false;
if(chips == 0)
{
won = true;
}
return won; // this is a stub - replace this!!!
} // method hasWon
/**
* Set the Hand object to the incoming Hand object (this comes from the
* Dealer)
*
* @param the hand dealt by the dealer
*/
public void setHand( Hand h )
{
} // method setHand
/**
* Return the player's name & the number of chips
*
* @return the players name & number of chips
*/
public String toString()
{
String nameChips;
nameChips = (name + totalChips);
return nameChips; // this is a stub only - replace this!!!
} // method toString
/**
* We won the hand, so increase chips
*
* @param the number of chips won
*/
public int winHand()
{
int chipsAB = 0;
//if(hand.beats(other))
{
chipsAB = getChips() + getBet();
}
//else
chipsAB = getChips() - getBet();
return chipsAB;
} // method winHand
}
答案 0 :(得分：1)
deck课程中的Deck成员未初始化 - 即null。
当您尝试通过引用deck[i]初始化其元素时，它将失败。要更正此问题，您只需初始化它：
private Card deck[] = new Card[CARDS_IN_DECK];