java - TicTacToe 游戏的 OutOfBoundsException；问题: arrays?

Question

我刚刚开始编写井字棋游戏。我刚刚运行它并得到以下堆栈跟踪:

 Exception in thread "main" java.lang.IndexOutOfBoundsException: Index: 0, Size: 0
 at java.util.ArrayList.rangeCheck(ArrayList.java:571)
 at java.util.ArrayList.get(ArrayList.java:349)
 at TicTacToe.isMarked(TicTacToe.java:23)
 at TicTacToe.mark(TicTacToe.java:59)
 at TicTacToe.main(TicTacToe.java:7)

我怀疑这是我的 ArrayList 设置方式有问题？我在某处读到过有关空值导致问题的内容，但这是我第一次处理数组，所以我不太熟悉这个主题。无论如何，这是我的代码:

    import java.util.*;

    public class TicTacToe {

    public static void main(String[] args) {
    newBoard();
    ******************System.out.println(mark(1));************
    System.out.println(mark(5));
    System.out.println(mark(9));
   }

 // Creates a blank board.
 public static ArrayList<String> newBoard() {
  ArrayList<String> board = new ArrayList<String>(8);
  return board;
 }

 // Returns true if the square has been marked.
 public static boolean isMarked(int numberOfSquare) {
  if (numberOfSquare > 9 || numberOfSquare < 1) {
   throw new IllegalArgumentException("Input a valid square number.");
  }
  ************if (newBoard().get(numberOfSquare - 1) == null) {***********
   return false;
  } else
   return true;
 }

 // Returns the number of moves that have been made.
 public static int moveCount() {
  return countMove();
 }

 // If called, adds 1 to number of moves.
 public static int countMove() {
  int moveNumber = 0;
  moveNumber++;
  return moveNumber;
 }

 // Checks for a win at the specified array location and player (X or O).
 public static boolean checkForWin(int x, int y, int z, int player) {
  if (player == 0) {
   return (newBoard().get(x)).equals("O")
     && (newBoard().get(y)).equals("O")
     && (newBoard().get(y)).equals("O");
  } else {
   return (newBoard().get(x)).equals("O")
     && (newBoard().get(y)).equals("O")
     && (newBoard().get(y)).equals("O");
  }
 }

 // Places an X or O on the specified square.
 public static boolean mark(int markSquareNumber) {
  if (markSquareNumber > 9 || markSquareNumber < 1) {
   throw new IllegalArgumentException("Input a valid square number.");
  }
  ***********if (isMarked(markSquareNumber)) {*******************
   throw new IllegalArgumentException("Square is already marked.");
  }
  if (moveCount() % 2 != 0) {
   newBoard().add(markSquareNumber - 1, "X");
   countMove();
  } else {
   newBoard().add(markSquareNumber - 1, "O");
   countMove();
  }
  if (checkForWin(0, 1, 2, 1) || checkForWin(3, 4, 5, 1)
    || checkForWin(6, 7, 8, 1)) {
   System.out.println("Player-X just won horizontally!");
   return true;
  } else if (checkForWin(0, 3, 6, 1) || checkForWin(1, 4, 7, 1)
    || checkForWin(2, 5, 8, 1)) {
   System.out.println("Player-X just won vertically!");
   return true;
  } else if (checkForWin(0, 4, 5, 1) || checkForWin(2, 4, 6, 1)
    || checkForWin(0, 4, 8, 1)) {
   System.out.println("Player-X just won diagonally!");
   return true;
  }
  if (checkForWin(0, 1, 2, 0) || checkForWin(3, 4, 5, 0)
    || checkForWin(6, 7, 8, 0)) {
   System.out.println("Player-O just won horizontally!");
   return true;
  } else if (checkForWin(0, 3, 6, 0) || checkForWin(1, 4, 7, 0)
    || checkForWin(2, 5, 8, 0)) {
   System.out.println("Player-O just won vertically!");
   return true;
  } else if (checkForWin(0, 4, 5, 0) || checkForWin(2, 4, 6, 0)
    || checkForWin(0, 4, 8, 0)) {
   System.out.println("Player-O just won diagonally!");
   return true;
  } else
   return false;
 }
}

我只是在堆栈跟踪中出现的行旁边放了一大堆星号。如果有人能指出我哪里出错了，那就太好了，谢谢!

好的，这是在您提供了所有精彩输入后我想出的解决方案:(请仅将其用于教育和引用目的，如果您在的话，我不想被我的教授吼叫我的CS1410课，你抄我!!!)

//Written by JTN for Assignment7.3- CS1410; October 2010. 
import java.util.*;

public class TicTacToe {
private static int moveNumber = 0;
private static ArrayList<String> board = new ArrayList<String>(8);
    public static void main(String[] args) {
        newBoard();
        mark(1);mark(2);
        mark(5);mark(3);
        mark(9);
        boardString();
    }
    // Returns the number of moves that have been made.
    public static int moveCount() {
        return (countMove()-1);
    }

    // If called, adds 1 to number of moves.
    public static int countMove() {
        moveNumber= moveNumber + 1;
        return moveNumber;
    }
    // Creates a blank board.
    public static ArrayList<String> newBoard() {
        for (int i = 0; i <= 8; i++)
            board.add("_");
        return board;
    }

    // Returns true if the square has been marked.
    public static boolean isMarked(int numberOfSquare) {
        if (numberOfSquare > 9 || numberOfSquare < 1) {
            throw new IllegalArgumentException("Input a valid square number.");
        }
        if ((board.get(numberOfSquare - 1)).equals("_")) {
            return false;
        } else
            return true;
    }



    // Checks for a win at the specified array location and player (X or O).
    public static boolean checkForWin(int x, int y, int z, int player) {
        if (player == 0) {
            return     (board.get(x)).equals("O")
                    && (board.get(y)).equals("O")
                    && (board.get(z)).equals("O");
        } 
        else {
            return     (board.get(x)).equals("X")
                    && (board.get(y)).equals("X")
                    && (board.get(z)).equals("X");
        }
    }

    // Places an X or O on the specified square.
    public static boolean mark(int markSquareNumber) {
        if (markSquareNumber > 9 || markSquareNumber < 1) {
            throw new IllegalArgumentException("Input a valid square number.");
        }
        if (isMarked(markSquareNumber)) {
            throw new IllegalArgumentException("Square is already marked.");
        }       
        if ((countMove() % 2) == 0){
            board.set(markSquareNumber - 1, "O");
        }
        else {
            board.set(markSquareNumber - 1, "X");
        } 

        if (checkForWin(0, 1, 2, 1) || checkForWin(3, 4, 5, 1)
                || checkForWin(6, 7, 8, 1)) {
            System.out.println("Player-X just won horizontally!");
            return true;
        } else if (checkForWin(0, 3, 6, 1) || checkForWin(1, 4, 7, 1)
                || checkForWin(2, 5, 8, 1)) {
            System.out.println("Player-X just won vertically!");
            return true;
        } else if (checkForWin(0, 4, 5, 1) || checkForWin(2, 4, 6, 1)
                || checkForWin(0, 4, 8, 1)) {
            System.out.println("Player-X just won diagonally!");
            return true;
        }
         else if (checkForWin(0, 1, 2, 0) || checkForWin(3, 4, 5, 0)
                || checkForWin(6, 7, 8, 0)) {
            System.out.println("Player-O just won horizontally!");
            return true;
        } else if (checkForWin(0, 3, 6, 0) || checkForWin(1, 4, 7, 0)
                || checkForWin(2, 5, 8, 0)) {
            System.out.println("Player-O just won vertically!");
            return true;
        } else if (checkForWin(0, 4, 5, 0) || checkForWin(2, 4, 6, 0)
                || checkForWin(0, 4, 8, 0)) {
            System.out.println("Player-O just won diagonally!");
            return true;
        } else
            return false;
    }

    public static String boardString(){
        String row1 = board.get(0)+"|"+board.get(1)+"|"+board.get(2);
        String row2 = board.get(3)+"|"+board.get(4)+"|"+board.get(5);
        String row3 = board.get(6)+"|"+board.get(7)+"|"+board.get(8);
        System.out.println(row1);
        System.out.println(row2);
        System.out.println(row3);
        return row1+row2+row3;
    }
}

Answer 1

这一行

ArrayList<String> board = new ArrayList<String>(8);

不会创建 8 个字符串的数组(或者 9 个字符串，如果这是有意的话)。它将创建一个 ArrayList，其初始容量为 8 个元素，但大小为 0。

为面板创建 ArrayList 后，您必须使用 add 方法向其中填充元素。尝试做类似的事情:

public static ArrayList<String> newBoard() {
    ArrayList<String> board = new ArrayList<String>(8);
    for (int i = 0; i < 9; i++)
        board.add("");
    return board;
}

消息 Exception in thread "main"java.lang.IndexOutOfBoundsException: Index: 0, Size: 0 表示您正在尝试访问长度为 0 的列表中的第 0 个元素(在没有元素的列表)。

此外，还有以下行:

newBoard().add(markSquareNumber - 1, "X");

应该是

newBoard().set(markSquareNumber - 1, "X");