Tic Tac Toe程序返回java.lang.NullPointerException

我的任务是制作一个井字游戏。我认为我的代码看起来不错，可以编译，但它返回：

"Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at TicTacModel.squareClicked(TicTacModel.java:33)
at TicTacGUI$ButtonListener.gridButtonClicked(TicTacGUI.java:79)
at TicTacGUI$ButtonListener.actionPerformed(TicTacGUI.java:53)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2018)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2341)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)
at java.awt.Component.processMouseEvent(Component.java:6505)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3321)
at java.awt.Component.processEvent(Component.java:6270)
at java.awt.Container.processEvent(Container.java:2229)
at java.awt.Component.dispatchEventImpl(Component.java:4861)
at java.awt.Container.dispatchEventImpl(Container.java:2287)
at java.awt.Component.dispatchEvent(Component.java:4687)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4832)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4492)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4422)
at java.awt.Container.dispatchEventImpl(Container.java:2273)
at java.awt.Window.dispatchEventImpl(Window.java:2719)
at java.awt.Component.dispatchEvent(Component.java:4687)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:735)
at java.awt.EventQueue.access$200(EventQueue.java:103)
at java.awt.EventQueue$3.run(EventQueue.java:694)
at java.awt.EventQueue$3.run(EventQueue.java:692)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
at java.awt.EventQueue$4.run(EventQueue.java:708)
at java.awt.EventQueue$4.run(EventQueue.java:706)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:705)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:242)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:161)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:150)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:146)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:138)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:91)

我的问题：我在做什么导致这个错误？ 我的老师给了我没有源代码的GUI课程。此外，我不允许替换/修改主类或GUI类。 这是我的TictaToe逻辑课程：

public class TicTacModel
{
// Instance Variables.
// You will need to include two 2-D Arrays.
// - one 2-D Array of String objects which remembers the marks on the "game board",
// - another 2-D Array of booleans which will tell the GUI what squares to mark in red. (true = red)
private String[][] marks;
private boolean[][] red;


//Your 2-D Arrays are not full of integer values, so java will not supply reliable defaults.
//Use the constructor to fill them with approprate default values.
public TicTacModel()
{
    boolean[][] red = {{false, false, false},
                       {false, false, false},
                       {false, false, false}};
    String[][] marks = {{" ", " ", " "},
                        {" ", " ", " "},
                        {" ", " ", " "}};
}

//Each time a square is clicked, the GUI will send the location of the click
//and the mark made ("X" or "O"). Record this informaion in your instance 2-D Array of Strings.
public void squareClicked(int row, int col, String mark)
{
    marks[col][row] = mark;
}


//Determine if the 2-D Array of Strings is full of "X"s and "O"s from the GUI.
//Return true if it is full, false otherwise.
public boolean isFull()
{
   int x, y = 0;
   for (x = 0; x <= 2; x++)
   {
       for (y = 0; y <= 2; y++)
       {
           if (marks[x][y] == " ")
           {
               return false;
           }
       }
   }
   return true;
}

//This method will require the most code.
//Check all possible ways there could be a winner.
//Return true if there is a winner, false otherwise.
//Set the corresponding elements of the instance boolean 2-D Array to true.
public boolean isWinner()
{
   if (marks[0][0] == marks[1][0] && marks[0][0] == marks[2][0]) 
   {
       red[0][0] = true;
       red[1][0] = true;
       red[2][0] = true;
       return true;
   }
   else if (marks[0][0] == marks[0][1] && marks[0][0] == marks[0][2])
   {
       red[0][0] = true;
       red[0][1] = true;
       red[0][2] = true;
       return true;
   }
   else if (marks[0][0] == marks[1][1] && marks[0][0] == marks[2][2])
   {
       red[0][0] = true;
       red[1][1] = true;
       red[2][2] = true;
       return true;
   }
   else if (marks[0][1] == marks[1][1] && marks[0][1] == marks[2][1])
   {
       red[0][1] = true;
       red[1][1] = true;
       red[2][1] = true;
       return true;
   }
   else if (marks[0][2] == marks[1][2] && marks[0][2] == marks[2][2])
   {
       red[0][2] = true;
       red[1][2] = true;
       red[2][2] = true;
       return true;
   }
   else if (marks[1][0] == marks[1][1] && marks[1][0] == marks[1][2])
   {
       red[1][0] = true;
       red[1][1] = true;
       red[1][2] = true;
       return true;
   }
   else if (marks[2][0] == marks[2][1] && marks[2][0] == marks[2][2])
   {
       red[2][0] = true;
       red[2][1] = true;
       red[2][2] = true;
       return true;
   }
   else if (marks[2][0] == marks[1][1] && marks[2][0] == marks[0][2])
   {
       red[2][0] = true;
       red[1][1] = true;
       red[0][2] = true;
       return true;
   }
   else return false;
}

//A getter method which returns the instance 2-D Array of booleans.
//Corresponding elements containing 'true' will be shaded red by the GUI.
public boolean[][] getRedSquares()
{    
    return red;
}

}

公共类模型
{
//实例变量。
//您需要包括两个二维阵列。
//-一个二维字符串对象数组，可记住“游戏板”上的标记，
//-另一个2-D布尔数组，它将告诉GUI用红色标记哪些方块。（真=红色）
专用字符串[][]标记；
私有布尔[][]红色；
//您的二维数组中没有完整的整数值，因此java不会提供可靠的默认值。
//使用构造函数用适当的默认值填充它们。
公共模型（）
{
布尔[][]红色={{false，false，false}，
{假，假，假}，
{假，假，假}；
字符串[][]标记={{{，''，''}，
{" ", " ", " "},
{" ", " ", " "}};
}
//每次单击正方形时，GUI都会发送单击的位置
//以及标记（“X”或“O”）。将此信息记录在您的实例2-D字符串数组中。
公共虚线（整行、整列、字符串标记）
{
标记[列][行]=标记；
}
//从GUI确定字符串的二维数组中是否充满了“X”和“O”。
//如果已满则返回true，否则返回false。
公共布尔值isFull（）
{
int x，y=0；
对于（x=0；x通过在构造函数中重新声明标记和红色变量来隐藏它们。这将初始化构造函数本地的变量，使实例字段为空。解决方案：不要重新声明变量。
通过在构造函数中重新声明标记和红色变量来隐藏它们。这将导致将初始化构造函数的局部变量，将实例字段保留为空。解决方案：不要重新声明该变量。
您的问题是您没有初始化
标记
。在构造函数中，您声明了一个名为
标记
的局部变量，但全局变量保持为空。按如下方式更改构造函数：

public TicTacModel()
{
  red = {{false, false, false},
                   {false, false, false},
                   {false, false, false}};
  marks = {{" ", " ", " "},
                    {" ", " ", " "},
                    {" ", " ", " "}};
}

您的问题是没有初始化
标记
。在构造函数中，您声明了一个名为
标记
的局部变量，但全局变量保持为空。请按如下方式更改构造函数：

public TicTacModel()
{
  red = {{false, false, false},
                   {false, false, false},
                   {false, false, false}};
  marks = {{" ", " ", " "},
                    {" ", " ", " "},
                    {" ", " ", " "}};
}

好的，当我将代码更改为该值时，
红色
和
标记
变量声明前面会出现一个“表达式非法开始”错误。为了解决这个问题，我在数组类的开头声明变量时，只给数组分配了变量。谢谢！好的，当我将代码更改为该值时，“表达式非法开始”在
红色
和
标记
变量声明前面出现错误。为了解决此问题，我在数组类的开头声明时，只为数组分配了变量。谢谢！