Its throwing the exception on the if statement within the checkAdjacent method, but it traces back to the checkWinner method. none of the objects in checkAdjacent are set to null, so something else must be. maybe one of the JButtons objects? Is is as simple as a null object? should i just be trying to handle the exception instead?
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)
