我是该网站的新用户。 最近我开始研究java游戏（Blackjack），我遇到了一些困难。这次我需要你的帮助。
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at Game.hitPlayer(Game.java:263)
at Game.deal(Game.java:235)
at Game.actionPerformed(Game.java:169)
at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.setPressed(Unknown Source)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(Unknown Source)
at java.awt.Component.processMouseEvent(Unknown Source)
at javax.swing.JComponent.processMouseEvent(Unknown Source)
at java.awt.Component.processEvent(Unknown Source)
at java.awt.Container.processEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Window.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$500(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)
这就是代码本身：
public class Game extends JFrame implements ActionListener {
private static final long serialVersionUID = 1L;
private JFrame frmBlackjack;
private JButton btnDeal = new JButton("DEAL HAND");
private JButton btnHit = new JButton("HIT");
private JButton btnStand = new JButton("STAND");
private final JLabel lblBet = new JLabel("Place your bet:");
private JTextField textField;
public JPanel dealerPanel = new JPanel();
public JPanel playerPanel = new JPanel();
public JLabel lblStatus = new JLabel("");
public JLabel lblDealer = new JLabel("Dealer:");
public JLabel lblPlayer = new JLabel("Player:");
public JLabel lblMoney = new JLabel("Money: 100$");
private Hand playerHand;
private Hand dealerHand;
private Deck deck;
private Card newCard;
private Double money = 100.0;
private Double bet = 0.0;
/**
* Launch the application.
*/
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
Game window = new Game();
window.frmBlackjack.setVisible(true);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
/**
* Create the application.
*/
public Game()
{
initialize();
}
/**
* Initialize the contents of the frame.
*/
private void initialize()
{
frmBlackjack = new JFrame();
frmBlackjack.getContentPane().setFont(new Font("Tahoma", Font.PLAIN, 11));
frmBlackjack.setTitle("Blackjack (21)");
frmBlackjack.setBounds(100, 100, 600, 520);
frmBlackjack.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frmBlackjack.getContentPane().setLayout(null);
btnDeal.setFont(new Font("Tahoma", Font.BOLD, 11));
btnDeal.setBounds(10, 410, 150, 60);
btnDeal.addActionListener(this);
frmBlackjack.getContentPane().add(btnDeal);
btnDeal.setEnabled(false);
btnHit.setFont(new Font("Tahoma", Font.BOLD, 11));
btnHit.setBounds(264, 410, 150, 60);
btnHit.addActionListener(this);
frmBlackjack.getContentPane().add(btnHit);
btnHit.setEnabled(false);
btnStand.setFont(new Font("Tahoma", Font.BOLD, 11));
btnStand.setBounds(424, 410, 150, 60);
btnStand.addActionListener(this);
frmBlackjack.getContentPane().add(btnStand);
btnStand.setEnabled(false);
dealerPanel.setBounds(113, 11, 440, 160);
frmBlackjack.getContentPane().add(dealerPanel);
dealerPanel.setLayout(new FlowLayout(FlowLayout.CENTER, 5, 5));
playerPanel.setBounds(113, 185, 440, 160);
frmBlackjack.getContentPane().add(playerPanel);
playerPanel.setLayout(new FlowLayout(FlowLayout.CENTER, 5, 5));
lblStatus.setFont(new Font("Agency FB", Font.PLAIN, 30));
lblStatus.setHorizontalAlignment(SwingConstants.CENTER);
lblStatus.setBounds(339, 351, 220, 50);
frmBlackjack.getContentPane().add(lblStatus);
lblDealer.setHorizontalAlignment(SwingConstants.CENTER);
lblDealer.setFont(new Font("Agency FB", Font.PLAIN, 20));
lblDealer.setBounds(10, 64, 93, 50);
frmBlackjack.getContentPane().add(lblDealer);
lblPlayer.setFont(new Font("Agency FB", Font.PLAIN, 20));
lblPlayer.setHorizontalAlignment(SwingConstants.CENTER);
lblPlayer.setBounds(10, 245, 93, 50);
frmBlackjack.getContentPane().add(lblPlayer);
lblMoney.setFont(new Font("Agency FB", Font.PLAIN, 20));
lblMoney.setHorizontalAlignment(SwingConstants.LEFT);
lblMoney.setBounds(40, 349, 75, 50);
frmBlackjack.getContentPane().add(lblMoney);
lblBet.setHorizontalAlignment(SwingConstants.CENTER);
lblBet.setFont(new Font("Agency FB", Font.PLAIN, 20));
lblBet.setBounds(135, 351, 100, 50);
frmBlackjack.getContentPane().add(lblBet);
textField = new JTextField();
textField.setBounds(245, 368, 45, 20);
frmBlackjack.getContentPane().add(textField);
textField.setColumns(10);
textField.addActionListener(this);
textField.setEnabled(true);
}
@Override
public void actionPerformed(ActionEvent e)
{
if (e.getSource() == btnHit)
{
hitPlayer();
if (playerHand.getBlackjackValue() > 21)
{
checkWinner();
btnHit.setEnabled(false);
btnStand.setEnabled(false);
btnDeal.setEnabled(false);
}
}
if (e.getSource() == btnStand)
{
while (dealerHand.getBlackjackValue() < 17 || playerHand.getBlackjackValue() > dealerHand.getBlackjackValue())
{
hitDealer();
}
checkWinner();
btnHit.setEnabled(false);
btnStand.setEnabled(false);
btnDeal.setEnabled(false);
}
if (e.getSource() == btnDeal)
{
deal();
lblStatus.setText("");
btnHit.setEnabled(true);
btnStand.setEnabled(true);
btnDeal.setEnabled(false);
}
if (e.getSource() == textField)
{
String curBet = textField.getText();
bet = Double.parseDouble(curBet);
textField.setEnabled(false);
btnDeal.setEnabled(true);
}
}
private void checkWinner()
{
dealerPanel.removeAll();
for (int i = 0; i < dealerHand.getCardCount(); i++)
{
dealerPanel.add(new JLabel(new ImageIcon("C:/Users/Talker/Desktop/cards/" + dealerHand.getCard(i).toString() + ".png")));
}
textField.setEnabled(true);
if (playerHand.getBlackjackValue() > 21)
{
lblStatus.setText("You Lost! (Over 21)");
money -= bet;
lblMoney.setText("Money:" + money + "$.");
}
else if (dealerHand.getBlackjackValue() > 21)
{
lblStatus.setText("Dealer Lost! (Over 21)");
money += bet;
lblMoney.setText("Money:" + money + "$.");
}
else if (dealerHand.getBlackjackValue() < playerHand.getBlackjackValue())
{
lblStatus.setText("You Won!");
money += bet;
lblMoney.setText("Money:" + money + "$.");
}
else if (dealerHand.getBlackjackValue() > playerHand.getBlackjackValue())
{
lblStatus.setText("Dealer Won!");
money -= bet;
lblMoney.setText("Money:" + money + "$.");
}
else
lblStatus.setText("It's a tie!");
}
private void deal()
{
playerPanel.removeAll();
dealerPanel.removeAll();
playerPanel.updateUI();
dealerPanel.updateUI();
//playerHand.clear();
//dealerHand.clear();
if (deck == null || deck.cardsLeft() < 15)
{
deck = new Deck();
deck.shuffleDeck();
}
hitPlayer();
hitDealerDown();
dealerHand.addCard(getNewCard());
hitPlayer();
hitDealer();
//Check for blackjack!
if(dealerHand.getBlackjackValue() == 21 && dealerHand.getBlackjackValue() != playerHand.getBlackjackValue())
{
lblStatus.setText("Blackjack! You Lost!");
money -= bet;
lblMoney.setText("Money:" + money + "$.");
}
if(playerHand.getBlackjackValue() == 21 && playerHand.getBlackjackValue() != dealerHand.getBlackjackValue())
{
lblStatus.setText("Blackjack! You Won!");
money = bet + bet/2;
lblMoney.setText("Money:" + money + "$.");
}
if(dealerHand.getBlackjackValue() == 21 && playerHand.getBlackjackValue() == 21)
lblStatus.setText("It's a tie!");
}
private void hitPlayer()
{
Card newCard = deck.dealCard();
playerHand.addCard(newCard);
playerPanel.add(new JLabel(new ImageIcon("C:/Users/Talker/Desktop/cards/" + newCard.toString() + ".png")));
playerPanel.updateUI();
}
private void hitDealerDown()
{
setNewCard(deck.dealCard());
dealerPanel.add(new JLabel(new ImageIcon("C:/Users/Talker/Desktop/cards/b2fv.png")));
dealerPanel.updateUI();
}
private void hitDealer()
{
Card newCard = deck.dealCard();
dealerHand.addCard(newCard);
dealerPanel.add(new JLabel(new ImageIcon("C:/Users/Talker/Desktop/cards/" + newCard.toString() + ".png")));
dealerPanel.updateUI();
}
public Card getNewCard() {
return newCard;
}
public void setNewCard(Card newCard) {
this.newCard = newCard;
}
}
有什么问题？我不明白！
答案 0 :(得分：0)
您需要在Game构造函数中（或在您从构造函数调用的initialize（）方法中）初始化实例变量（playerHand，dealerHand，deck等）。您将获得NullPointerException，因为（非原始）实例变量的默认（未初始化）值为null。