java - 井字游戏 NullPointerException

Question

好吧，我正在玩井字棋，在我放入 checkWin() 方法之前，它开始得很好。一旦我把它放进去，每次我点击一个通常放置 X 或 O 的方 block 时，它都会给我一个错误 NullPointerException。我相信代码中所说的，如果 boolean 二维数组“板”为假，那么胜利就会发生，但当我没有感叹号品脱时也会发生这种情况。有人可以帮忙吗？谢谢。

public Boolean[][] board= new Boolean[3][3];
public boolean xTurn = true;

public void setup() {
  size(900, 900);
  background(255);
  strokeWeight(2);
  line(300, 0, 300, 900);
  line(600, 0, 600, 900);
  line(0, 300, 900, 300);
  line(0, 600, 900, 600);
}

public void draw() {

}

public void mouseClicked() {
  if (xTurn) {
    xTurn();
  }
  else if (!xTurn) {
    oTurn();
  }
}

public void xTurn() {
  if (mouseX > 0 && mouseX < 300 && mouseY > 0 && mouseY < 300 && board[0][0] == null) {
    stroke(255, 0, 0);
    line(50, 250, 250, 50);
    line(250, 250, 50, 50);
    board[0][0] = true;
    xTurn = false;
    checkWin();
  }
  else if (mouseX > 300 && mouseX < 600 && mouseY > 0 && mouseY < 300 && board[0][1] == null) {
    stroke(255, 0, 0);
    line(350, 250, 550, 50);
    line(550, 250, 350, 50);
    board[0][1] = true;
    xTurn = false;
    checkWin();
  }
  else if (mouseX > 600 && mouseX < 900 && mouseY > 0 && mouseY < 300 && board[0][2] == null) {
    stroke(255, 0, 0);
    line(650, 50, 850, 250);
    line(650, 250, 850, 50);
    board[0][2] = true;
    xTurn = false;
    checkWin();
  }
  else if (mouseX > 0 && mouseX < 300 && mouseY > 300 && mouseY < 600 && board[1][0] == null) {
    stroke(255, 0, 0);
    line(50, 550, 250, 350);
    line(250, 550, 50, 350);
    board[1][0] = true;
    xTurn = false;
    checkWin();
  }
  else if (mouseX > 300 && mouseX < 600 && mouseY > 300 && mouseY < 600 && board[1][1] == null) {
    stroke(255, 0, 0);
    line(350, 550, 550, 350);
    line(550, 550, 350, 350);
    board[1][1] = true;
    xTurn = false;
    checkWin();
  }
  else if (mouseX > 600 && mouseX < 900 && mouseY > 300 && mouseY < 600 && board[1][2] == null) {
    stroke(255, 0, 0);
    line(650, 350, 850, 550);
    line(650, 550, 850, 350);
    board[1][2] = true;
    xTurn = false;
    checkWin();
  }
  else if (mouseX > 0 && mouseX < 300 && mouseY > 600 && mouseY < 900 && board[2][0] == null) {
    stroke(255, 0, 0);
    line(50, 850, 250, 650);
    line(250, 850, 50, 650);
    board[2][0] = true;    
    xTurn = false;
    checkWin();
  }
  else if (mouseX > 300 && mouseX < 600 && mouseY > 600 && mouseY < 900 && board[2][1] == null) {
    stroke(255, 0, 0);
    line(350, 850, 550, 650);
    line(550, 850, 350, 650);
    board[2][1] = true;
    xTurn = false;
    checkWin();
  }
  else if (mouseX > 600 && mouseX < 900 && mouseY > 600 && mouseY < 900 && board[2][2] == null) {
    stroke(255, 0, 0);
    line(650, 650, 850, 850);
    line(650, 850, 850, 650);
    board[2][2] = true;
    xTurn = false;
    checkWin();
  }
}

public void oTurn() {
  if (mouseX > 0 && mouseX < 300 && mouseY > 0 && mouseY < 300 && board[0][0] == null) {
     stroke(0, 0, 255);
     ellipse(150, 150, 200, 200);
     board[0][0] = false;
     xTurn = true;
     checkWin();
  }
  else if (mouseX > 300 && mouseX < 600 && mouseY > 0 && mouseY < 300 && board[0][1] == null) {
     stroke(0, 0, 255);
     ellipse(450, 150, 200, 200);
     board[0][1] = false;
     xTurn = true;
     checkWin();
  }
  else if (mouseX > 600 && mouseX < 900 && mouseY > 0 && mouseY < 300 && board[0][2] == null) {
     stroke(0, 0, 255);
     ellipse(750, 150, 200, 200);
     board[0][2] = false;
     xTurn = true;
     checkWin();
  }
  else if (mouseX > 0 && mouseX < 300 && mouseY > 300 && mouseY < 600 && board[1][0] == null) {
    stroke(0, 0, 255);
     ellipse(150, 450, 200, 200);
     board[1][0] = false;
     xTurn = true;
     checkWin();
  }
  else if (mouseX > 300 && mouseX < 600 && mouseY > 300 && mouseY < 600 && board[1][1] == null) {
    stroke(0, 0, 255);
     ellipse(450, 450, 200, 200);
     board[1][1] = false;
     xTurn = true;
     checkWin();
  }
  else if (mouseX > 600 && mouseX < 900 && mouseY > 300 && mouseY < 600 && board[1][2] == null) {
    stroke(0, 0, 255);
     ellipse(750, 450, 200, 200);
     board[1][2] = false;
     xTurn = true;
     checkWin();
  }
  else if (mouseX > 0 && mouseX < 300 && mouseY > 600 && mouseY < 900 && board[2][0] == null) {
    stroke(0, 0, 255);
     ellipse(150, 750, 200, 200);
     board[2][0] = false;
     xTurn = true;
     checkWin();
  }
  else if (mouseX > 300 && mouseX < 600 && mouseY > 600 && mouseY < 900 && board[2][1] == null) {
    stroke(0, 0, 255);
     ellipse(450, 750, 200, 200);
     board[2][1] = false;
     xTurn = true;
     checkWin();
  }
  else if (mouseX > 600 && mouseX < 900 && mouseY > 600 && mouseY < 900 && board[2][2] == null) {
    stroke(0, 0, 255);
     ellipse(750, 750, 200, 200);
     board[2][2] = false;
     xTurn = true;
     checkWin();
  }
}

public void checkWin() {
  if (!board[0][0] && !board[0][1] && !board[0][2]) {
    stroke(0, 255, 0);
    line(100, 150, 800, 150);
  }
}

Answer 1

 public Boolean[][] board= new Boolean[3][3];

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