它在checkAdjacent方法内的if语句上引发异常，但可追溯到checkWinner方法。 checkAdjacent中的所有对象均未设置为null，因此必须设置其他对象。也许是JButtons对象之一？像空对象一样简单吗？我应该只是尝试处理异常吗？
package tictactoeb;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.Icon;
import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
public class TicTacToe implements ActionListener
{
String check[] = new String[9];
JButton buttons[] = new JButton[9];
int num = 0;
ImageIcon X = new ImageIcon("X.png");
ImageIcon O = new ImageIcon("O.png");
JPanel layout = new JPanel();
JFrame window = new JFrame("TicTacToe");
String letter = " ";
ImageIcon img;
String winner;
public static void main(String[] args)
{
new TicTacToe();
}
public TicTacToe()
{
for(String s : check)
s = " ";
JFrame window = new JFrame("TicTacToe");
window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
window.setBounds(400,400,400,400);
window.setLayout(new GridLayout(3,3));
for(int i = 0; i <= 8; i++)
{
buttons[i] = new JButton(" ");
this.buttons[i] = buttons[i];
buttons[i].setIcon(null);
buttons[i].addActionListener(this);
window.add(buttons[i]);
}
window.setVisible(true);
}
@Override
public void actionPerformed(ActionEvent e)
{
JButton buttonClicked = (JButton)e.getSource();
if(num%2 == 0)
{
letter = "X";
img = X;
}
else
{
letter = "O";
img = O;
}
for(int i = 0;i<9; ++i)
if(buttonClicked.equals(buttons[i]))
{
buttons[i].setIcon(img);
check[i] = letter;
}
if(checkWinner(letter))
{
System.out.println("Winner");
clearBoard();
}
num++;
}
public boolean checkWinner(String ltr)
{
boolean ref = false;
if(checkAdjacent(0,1,ltr) && checkAdjacent(1,2,ltr))
ref = true;
else if(checkAdjacent(3,4,ltr) && checkAdjacent(4,5,ltr))
ref = true;
else if(checkAdjacent(6,7,ltr) && checkAdjacent(7,8,ltr))
ref = true;
else if(checkAdjacent(0,3,ltr) && checkAdjacent(3,6,ltr))
ref = true;
else if(checkAdjacent(1,4,ltr) && checkAdjacent(4,7,ltr))
ref = true;
else if(checkAdjacent(2,5,ltr) && checkAdjacent(5,8,ltr))
ref = true;
else if(checkAdjacent(0,4,ltr) && checkAdjacent(4,8,ltr))
ref = true;
else if(checkAdjacent(2,4,ltr) && checkAdjacent(4,6,ltr))
ref = true;
return ref;
}
public boolean checkAdjacent(int pos1,int pos2, String ltr)
{
boolean ref = false;
if(check[pos1].equals(ltr) && check[pos2].equals(ltr))
ref = true;
else
ref = false;
return ref;
}
public void clearBoard()
{
for(JButton i : buttons)
{
i.setIcon(null);
}
for(String c : check)
c = " ";
}
}
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at tictactoeb.TicTacToe.checkAdjacent(TicTacToe.java:109)
at tictactoeb.TicTacToe.checkWinner(TicTacToe.java:85)
at tictactoeb.TicTacToe.actionPerformed(TicTacToe.java:73)
at java.desktop/javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1967)
at java.desktop/javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2308)
at java.desktop/javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:405)
at java.desktop/javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:262)
at java.desktop/javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:279)
at java.desktop/java.awt.Component.processMouseEvent(Component.java:6636)
at java.desktop/javax.swing.JComponent.processMouseEvent(JComponent.java:3342)
at java.desktop/java.awt.Component.processEvent(Component.java:6401)
at java.desktop/java.awt.Container.processEvent(Container.java:2263)
at java.desktop/java.awt.Component.dispatchEventImpl(Component.java:5012)
at java.desktop/java.awt.Container.dispatchEventImpl(Container.java:2321)
at java.desktop/java.awt.Component.dispatchEvent(Component.java:4844)
at java.desktop/java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4918)
at java.desktop/java.awt.LightweightDispatcher.processMouseEvent(Container.java:4547)
at java.desktop/java.awt.LightweightDispatcher.dispatchEvent(Container.java:4488)
at java.desktop/java.awt.Container.dispatchEventImpl(Container.java:2307)
at java.desktop/java.awt.Window.dispatchEventImpl(Window.java:2762)
at java.desktop/java.awt.Component.dispatchEvent(Component.java:4844)
at java.desktop/java.awt.EventQueue.dispatchEventImpl(EventQueue.java:772)
at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:721)
at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:715)
at java.base/java.security.AccessController.doPrivileged(AccessController.java:391)
at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:85)
at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:95)
at java.desktop/java.awt.EventQueue$5.run(EventQueue.java:745)
at java.desktop/java.awt.EventQueue$5.run(EventQueue.java:743)
at java.base/java.security.AccessController.doPrivileged(AccessController.java:391)
at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:85)
at java.desktop/java.awt.EventQueue.dispatchEvent(EventQueue.java:742)
at java.desktop/java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:203)
at java.desktop/java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:124)
at java.desktop/java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:113)
at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:109)
at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
at java.desktop/java.awt.EventDispatchThread.run(EventDispatchThread.java:90)
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at tictactoeb.TicTacToe.checkAdjacent(TicTacToe.java:109)
at tictactoeb.TicTacToe.checkWinner(TicTacToe.java:85)
at tictactoeb.TicTacToe.actionPerformed(TicTacToe.java:73)
at java.desktop/javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1967)
at java.desktop/javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2308)
at java.desktop/javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:405)
at java.desktop/javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:262)
at java.desktop/javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:279)
at java.desktop/java.awt.Component.processMouseEvent(Component.java:6636)
at java.desktop/javax.swing.JComponent.processMouseEvent(JComponent.java:3342)
at java.desktop/java.awt.Component.processEvent(Component.java:6401)
at java.desktop/java.awt.Container.processEvent(Container.java:2263)
at java.desktop/java.awt.Component.dispatchEventImpl(Component.java:5012)
at java.desktop/java.awt.Container.dispatchEventImpl(Container.java:2321)
at java.desktop/java.awt.Component.dispatchEvent(Component.java:4844)
at java.desktop/java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4918)
at java.desktop/java.awt.LightweightDispatcher.processMouseEvent(Container.java:4547)
at java.desktop/java.awt.LightweightDispatcher.dispatchEvent(Container.java:4488)
at java.desktop/java.awt.Container.dispatchEventImpl(Container.java:2307)
at java.desktop/java.awt.Window.dispatchEventImpl(Window.java:2762)
at java.desktop/java.awt.Component.dispatchEvent(Component.java:4844)
at java.desktop/java.awt.EventQueue.dispatchEventImpl(EventQueue.java:772)
at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:721)
at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:715)
at java.base/java.security.AccessController.doPrivileged(AccessController.java:391)
at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:85)
at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:95)
at java.desktop/java.awt.EventQueue$5.run(EventQueue.java:745)
at java.desktop/java.awt.EventQueue$5.run(EventQueue.java:743)
at java.base/java.security.AccessController.doPrivileged(AccessController.java:391)
at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:85)
at java.desktop/java.awt.EventQueue.dispatchEvent(EventQueue.java:742)
at java.desktop/java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:203)
at java.desktop/java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:124)
at java.desktop/java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:113)
at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:109)
at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
at java.desktop/java.awt.EventDispatchThread.run(EventDispatchThread.java:90)