Java实现康威生命游戏：存活邻居计数异常问题求助

我是编程新手，在Java中实现康威生命游戏时遇到了邻居计数错误的问题。已知初始5x5棋盘如下（.代表死亡细胞，0代表存活细胞）：

. . . . .
. . . . .
. . 0 . .
. . . . .
. . . . .

我编写了countLivingNeighbors方法统计单个细胞周围的存活邻居数量，但可视化邻居数量后，结果不符合预期：

EXPECTED:           ACTUAL:
0 0 0 0 0           0 0 0 0 0
0 1 1 1 0           0 1 1 1 0
0 1 0 1 0           0 1 0 0 0
0 1 1 1 0           0 0 0 0 0
0 0 0 0 0           0 0 0 0 0

我发现countLivingNeighbors无法正确统计当前细胞左侧、左上、上方、右上方向的存活细胞，但自认为代码逻辑正确，希望得到帮助。

以下是完整的当前代码版本：

package GameOfLife;

import java.util.Random;

public class Main {

   public static void main(String[] args){
       int boardWidth = 5, boardHeight = 5;
       boolean[][] board = {{false, false, false, false, false},
                            {false, false, false, false, false},
                            {false, false, true , false, false},
                            {false, false, false, false, false},
                            {false, false, false, false, false}};

       renderBoard(board);

       System.out.println();

       board = getNextBoardState(board);
       renderBoard(board);
   }


   static boolean[][] createRandomBoard(int width, int height) {
       boolean[][] board = new boolean[height][width];

       for (int i = 0; i < height; i++) {
           for (int j = 0; j < width; j++) {
               switch (new Random().nextInt(2)) {
                   case 0 -> board[i][j] = false;
                   case 1 -> board[i][j] = true;
               }
           }
       }

       return board;
   }

   static void renderBoard(boolean[][] board) {
       for (boolean[] cellRows : board) {
           for (boolean cells : cellRows) {
               if (cells) System.out.print(" 0 ");
               else System.out.print(" . ");
           } System.out.println();
       }
   }

   static boolean[][] getNextBoardState(boolean[][] board) {
       boolean[][] nextBoard;
       nextBoard = board;

       for (int y = 0; y < board.length; y++) {
           for (int x = 0; x < board[0].length; x++) {
                int livingNeighbors = countLivingNeighbors(board, x, y);
                System.out.print(" " + livingNeighbors + " ");
                nextBoard[y][x] = setNextCellState(livingNeighbors, board[y][x]);
           } System.out.println();
       } System.out.println();

       return nextBoard;
   }

   static int countLivingNeighbors(boolean[][] board, int posX, int posY) {
       int counter = 0;

       for (int j = -1; j < 2; j++) {
           if (posY + j < 0 || posY + j >= board.length) continue;
           for (int i = -1; i < 2; i++) {
               if (posX + i < 0 || posX + i >= board[0].length) continue;
               if (board[posY + j][posX + i]) ++counter;
           }
       }

       if (board[posY][posX]) --counter;
       return counter;
   }

   static boolean setNextCellState(int livingNeighbors, boolean cellState) {
       if (cellState) {
           if (livingNeighbors <= 1 || livingNeighbors > 3) return false;
       } else {
           if (livingNeighbors == 3) return true;
       }

       return cellState;
   }
}

问题分析与解决方案 #

问题根本不在countLivingNeighbors方法里，而是在getNextBoardState方法中：你直接将nextBoard赋值为board，这意味着两者指向同一个二维数组对象。当你修改nextBoard[y][x]时，实际上是在修改原board数组的内容，后续的countLivingNeighbors调用会读取到已经被修改过的细胞状态，导致邻居计数错误。

比如初始中间的存活细胞（坐标2,2）会因为邻居数不足被设置为死亡，当计算下方细胞（3,2）的邻居时，原中间细胞已经变成死亡状态，所以统计不到它，导致实际输出第三行之后的邻居数都是0。

修改方式：在getNextBoardState方法中创建一个全新的二维数组作为nextBoard，而非直接引用原数组：

static boolean[][] getNextBoardState(boolean[][] board) {
    // 创建和原数组大小一致的新数组
    boolean[][] nextBoard = new boolean[board.length][board[0].length];

    for (int y = 0; y < board.length; y++) {
        for (int x = 0; x < board[0].length; x++) {
             int livingNeighbors = countLivingNeighbors(board, x, y);
             System.out.print(" " + livingNeighbors + " ");
             nextBoard[y][x] = setNextCellState(livingNeighbors, board[y][x]);
        } System.out.println();
    } System.out.println();

    return nextBoard;
}

这样修改后，所有邻居计数都会基于原数组的初始状态计算，不会因为提前修改细胞状态干扰后续计算，邻居计数结果就能和预期一致。

内容的提问来源于stack exchange，提问作者Eugene Olete