网站建设 策划,学做网站的书籍,链网,汽车网站设计我在这里有一个错误,我不知道它来自哪里.我在初学者的java课程是高中,所以我在这里还没有太多的经验.我有3个相互合并的程序.我有一个卡片类,可以创建一张扑克牌//********************************************************************// Card.java Author: Lewis and Loftus…我在这里有一个错误,我不知道它来自哪里.我在初学者的java课程是高中,所以我在这里还没有太多的经验.我有3个相互合并的程序.我有一个卡片类,可以创建一张扑克牌//********************************************************************// Card.java Author: Lewis and Loftus//// Solution to Programming Project 4.5//********************************************************************import java.util.*;public class Card{public final static int ACE 1;public final static int TWO 2;public final static int THREE 3;public final static int FOUR 4;public final static int FIVE 5;public final static int SIX 6;public final static int SEVEN 7;public final static int EIGHT 8;public final static int NINE 9;public final static int TEN 10;public final static int JACK 11;public final static int QUEEN 12;public final static int KING 13;public final static int CLUBS 1;public final static int DIAMONDS 2;public final static int HEARTS 3;public final static int SPADES 4;private final static int NUM_FACES 13;private final static int NUM_SUITS 4;private int face,suit;private String faceName,suitName;private int myInt1,myInt2;Random rand new Random();//-----------------------------------------------------------------// Creates a random card.//-----------------------------------------------------------------public Card (){face rand.nextInt(4) 1;setFaceName();suit rand.nextInt(13) 1;setSuitName();}//-----------------------------------------------------------------// Sets the string representation of the face using its stored// numeric value.//-----------------------------------------------------------------private void setFaceName(){switch (face){case 1:faceName Ace;break;case 2:faceName Two;break;case 3:faceName Three;break;case 4:faceName Four;break;case 5:faceName Five;break;case 6:faceName Six;break;case 7:faceName Seven;break;case 8:faceName Eight;break;case 9:faceName Nine;break;case 10:faceName Ten;break;case 11:faceName Jack;break;case 12:faceName Queen;break;case 13:faceName King;break;}}//-----------------------------------------------------------------// Sets the string representation of the suit using its stored// numeric value.//-----------------------------------------------------------------private void setSuitName(){switch (suit){case 1:suitName Clubs;break;case 2:suitName Diamonds;break;case 3:suitName Hearts;break;case 4:suitName Spades;break;}}//-----------------------------------------------------------------// Determines if this card is higher than the passed card. The// second parameter determines if aces should be considered high// (beats a King) or low (lowest of all faces). Uses the suit// if both cards have the same face.//-----------------------------------------------------------------public boolean isHigherThan (Card card2,boolean aceHigh){boolean result false;if (face card2.getFace()){if (suit card2.getSuit())result true;}else{if (aceHigh face ACE)result true;elseif (face card2.getFace())result true;}return result;}//-----------------------------------------------------------------// Determines if this card is higher than the passed card,// assuming that aces should be considered high.//-----------------------------------------------------------------public boolean isHigherThan (Card card2){return isHigherThan (card2,true);}//-----------------------------------------------------------------// Returns the face (numeric value) of this card.//-----------------------------------------------------------------public int getFace (){return face;}//-----------------------------------------------------------------// Returns the suit (numeric value) of this card.//-----------------------------------------------------------------public int getSuit (){return suit;}//-----------------------------------------------------------------// Returns the face (string value) of this card.//-----------------------------------------------------------------public String getFaceName (){return faceName;}//-----------------------------------------------------------------// Returns the suit (string value) of this card.//-----------------------------------------------------------------public String getSuitName (){return suitName;}//-----------------------------------------------------------------// Returns the string representation of this card,including// both face and suit.//-----------------------------------------------------------------public String toString (){return faceName of suitName;}}我有一张Deck Of cards文件可以创建52张卡片import java.util.*;public class DeckOfCards{private Card deckOfCards[];private int currentCardUsed;private final int NumberOfCards 52;private int nextCard;private Random rand;String myString All Cards have been dealt.;public DeckOfCards(){deckOfCards new Card[NumberOfCards];currentCardUsed 0;Random rand new Random();for(int index 0; index deckOfCards.length; index ){deckOfCards[index] new Card();}}public void shuffleCards(){currentCardUsed 0;for(int newCard 0; newCard deckOfCards.length; newCard ){int nextCard rand.nextInt(NumberOfCards);Card temporaryDeck deckOfCards[newCard];deckOfCards[newCard] deckOfCards[nextCard];deckOfCards[nextCard] temporaryDeck;}}public Card dealCard(){if(currentCardUsed deckOfCards.length){return deckOfCards[currentCardUsed ];}else{return null;}}}最后我有一个司机班public class DeckTester{public static void main(String [] args){DeckOfCards deck new DeckOfCards();deck.shuffleCards();System.out.println(deck.dealCard());System.out.println(deck.dealCard());System.out.println(deck.dealCard());System.out.println(deck.dealCard());System.out.println(deck.dealCard());System.out.println(deck.dealCard());}}他们都没有错误.但是当我运行驱动程序时,我得到了输出Exception in thread main java.lang.NullPointerExceptionat DeckOfCards.shuffleCards(DeckOfCards.java:39)at DeckTester.main(DeckTester.java:8)我试过在交易方法中改变Null无济于事.
