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我正在試圖製作一個模擬紙牌遊戲戰爭的程序。空指針異常Java卡牌遊戲戰爭
類Project2的
package proj2;
import java.util.Scanner;
public class Project2 {
public static void main(String[ ] args)
{
Scanner keybd = new Scanner(System.in);
// Get player names
System.out.println("Welcome to WAR!!");
System.out.print("Please enter player 1's name: ");
String p1Name = keybd.nextLine();
System.out.print("Please enter player 2's name: ");
String p2Name = keybd.nextLine();
// Get random number generator (RNG) seed and initialize the game
System.out.print ("Please enter the RNG seed for shuffling: ");
long rngSeed = keybd.nextLong();
Game war = new Game(p1Name, p2Name, rngSeed);
int turn = 1;
// While game is being played, print details and results of each turn
while (!war.gameComplete())
{
System.out.printf("Turn %2d\n", turn);
System.out.println("-----");
System.out.println(war.nextTurn());
++turn;
}
// All turns complete; print the game results
System.out.println("Game Over!!");
System.out.println(war.gameResult());
}
}
類遊戲：
package proj2;
public class Game {
private Deck deck;
private Player player1;
private CardPile p1Deck;
private Player player2;
private CardPile p2Deck;
private int warCount;
private int turns;
public Game(String p1, String p2, long rngSeed)
{
this.deck = new Deck();
deck.Shuffle((int) rngSeed);
this.player1 = new Player(p1, 0, 0);
this.p1Deck = new CardPile(deck.Deal());
this.player2 = new Player(p2, 0, 0);
this.p2Deck = new CardPile(deck.Deal());
this.turns = 1;
this.warCount = 0;
}
public String nextTurn()
{
p1Card = p1Deck.drawCard();
(ERROR)---> String p1Turn = player1.getName() + " shows " + p1Card.cardString();
Card p2Card = p2Deck.drawCard();
String p2Turn = player2.getName() + " shows " + p2Card.cardString();
String winner = "";
if(p1Card.getValue() > p2Card.getValue())
{
Card[] wonCards = new Card[2];
wonCards[0] = p1Card;
wonCards[1] = p2Card;
p1Deck.addCard(wonCards, 2);
player1.setCardsWon(wonCards.length);
winner = player1.getName() + " wins 2 cards" ;
}
if(p2Card.getValue() > p1Card.getValue())
{
Card[] wonCards = new Card[2];
wonCards[0] = p2Card;
wonCards[1] = p1Card;
p1Deck.addCard(wonCards, 2);
player2.setCardsWon(wonCards.length);
winner = "/n" + player2.getName() + " wins 2 cards";
}
String warTurn = "";
if(p1Card.getValue() == p2Card.getValue())
{
this.warCount = warCount + 1;
warTurn = "WAR!!";
Card[] wonCards = new Card[8];
while(p1Card.getValue() != p2Card.getValue())
{
wonCards[0] = p1Deck.drawCard();
wonCards[2] = p1Deck.drawCard();
wonCards[4] = p1Deck.drawCard();
Card p1WarCard = p1Deck.drawCard();
wonCards[6] = p1WarCard;
wonCards[1] = p2Deck.drawCard();
wonCards[3] = p2Deck.drawCard();
wonCards[5] = p2Deck.drawCard();
Card p2WarCard = p2Deck.drawCard();
wonCards[7] = p2WarCard;
if(p1WarCard.getValue() > p2WarCard.getValue())
{
p1Deck.addCard(wonCards, wonCards.length);
player1.setCardsWon(wonCards.length);
}
if(p2WarCard.getValue() > p2WarCard.getValue())
{
p2Deck.addCard(wonCards, wonCards.length);
player2.setCardsWon(wonCards.length);
}
}
}
String turnResults = p1Turn + "/n" + p2Turn + "/n" + warTurn + winner;
return turnResults;
}
public boolean gameComplete()
{
boolean result = false;
if(turns == 20) {
result = true;
}
return result;
}
public String gameResult()
{
String p1Result = (player1.getName() + " won " + player1.getCardsWon() + "and"
+ player1.getWarsWon() + "war(s)" + "/n");
String p2Result = (player2.getName() + " won " + player2.getCardsWon() + "and"
+ player1.getWarsWon() + "war(s)" + "/n");
String winner = "";
if(player1.getCardsWon() > player2.getCardsWon())
{
winner = "Winner: " + player1.getName();
}
if(player2.getCardsWon() < player2.getCardsWon())
{
winner = "Winner: " + player2.getName();
}
if(player1.getCardsWon() == player2.getCardsWon())
{
winner = "Game is a draw";
}
String finalResult = ("Game Over!!" + "There were " + warCount
+ "war(s)" + p1Result + "/n" + p2Result + "/n" + winner);
return finalResult;
}
}
當我試圖訪問類的卡，我得到一個空指針異常錯誤。我不確定是什麼導致了錯誤。
public class Card {
private char rank;
private String suit;
private int value;
public Card(char rank, String suit, int value)
{
this.rank = rank;
this.suit = suit;
this.value = value;
}
public char getRank()
{
return rank;
}
public String getSuit()
{
return suit;
}
public int getValue()
{
return value;
}
public String cardString()
{
String card = (rank + " of " + suit);
return card;
}
}
我試着用google搜索解決方案，它告訴我在引用對象之前初始化對象。我嘗試初始化，但它仍然產生空指針異常錯誤。
我得到的錯誤是這個。
Exception in thread "main" java.lang.NullPointerException
at proj2.Game.nextTurn(Game.java:29)
at proj2.Project2.main(Project2.java:37)
drawCard（）方法來自這個類。
package proj2;
public class CardPile {
private Card[] playerDeck;
public CardPile(Card[] deck)
{
this.playerDeck = deck;
}
public Card drawCard()
{
Card topCard = playerDeck[0];
Card[] newPlayerDeck = new Card[playerDeck.length - 1];
int counter = 0;
for(int i = 1; i < playerDeck.length; i++)
{
newPlayerDeck[counter] = playerDeck[i];
counter++;
}
this.playerDeck = newPlayerDeck;
return topCard;
}
}
那麼哪一行會拋出異常？ – Jason
請發佈您的stacktrace的相關部分 –
另外，您的'Deck.drawCard'返回的是什麼？ – Amadan