Java:防止数组越界

Question

我正在开发一款跳棋游戏，如果您想了解更多信息，可以在这里查看； http://minnie.tuhs.org/I2P/Assessment/assig2.html

当我进行测试以查看玩家是否能够从当前位置到达网格上的某个方 block (即 +1 +1、+1 -1 等)时，我得到一个 java.lang .ArrayIndexOutOfBoundsException 错误。

这是我用来进行移动的代码；

public static String makeMove(String move, int playerNumber)
   {
       // variables to contain the starting and destination coordinates, subtracting 1 to match array size
       int colStart = move.charAt(1) - FIRSTCOLREF - 1;
       int rowStart = move.charAt(0) - FIRSTROWREF - 1;
       int colEnd   = move.charAt(4) - FIRSTCOLREF - 1;
       int rowEnd   = move.charAt(3) - FIRSTROWREF - 1;


       // variable to contain which player is which
       char player, enemy;
       if (playerNumber==1)
        {
            player= WHITEPIECE;
            enemy=  BLACKPIECE;
        }
       else
        {
            player= BLACKPIECE;
            enemy=  WHITEPIECE;
        }

        // check that the starting square contains a player piece
        if (grid [ colStart ] [ rowStart ] == player)
        {
            // check that the player is making a diagonal move
            if (grid [ colEnd ] [ rowEnd ] == grid [ (colStart++) ] [ (rowEnd++) ] &&
                grid [ colEnd ] [ rowEnd ] == grid [ (colStart--) ] [ (rowEnd++) ] &&
                grid [ colEnd ] [ rowEnd ] == grid [ (colStart++) ] [ (rowEnd--) ] &&
                grid [ colEnd ] [ rowEnd ] == grid [ (colStart--) ] [ (rowEnd--) ])
                {
                    // check that the destination square is free
                    if (grid [ colEnd ] [ rowEnd ] == BLANK)
                    {
                        grid [ colStart ] [ rowStart ] = BLANK;
                        grid [ colEnd ] [ rowEnd ]     = player;

                    }
                }
            // check if player is jumping over a piece
            else if (grid [ colEnd ] [ rowEnd ] == grid [ (colStart+2) ] [ (rowEnd+2) ] &&
                     grid [ colEnd ] [ rowEnd ] == grid [ (colStart-2) ] [ (rowEnd+2) ] &&
                     grid [ colEnd ] [ rowEnd ] == grid [ (colStart+2) ] [ (rowEnd-2) ] &&
                     grid [ colEnd ] [ rowEnd ] == grid [ (colStart-2) ] [ (rowEnd-2) ])
                 {
                   // check that the piece in between contains an enemy
                    if ((grid [ (colStart++) ] [ (rowEnd++) ] == enemy ) &&
                        (grid [ (colStart--) ] [ (rowEnd++) ] == enemy ) &&
                        (grid [ (colStart++) ] [ (rowEnd--) ] == enemy ) &&
                        (grid [ (colStart--) ] [ (rowEnd--) ] == enemy ))
                    {
                        // check that the destination is free
                        if (grid [ colEnd ] [ rowEnd ] == BLANK)
                        {
                            grid [ colStart ] [ rowStart ] = BLANK;
                            grid [ colEnd ] [ rowEnd ]     = player;
                        }

                    }
                 }

        }

我不确定如何防止错误发生，您有什么建议？

Answer 1

首先想到的是在 if 语句条件中间使用后增量表达式，例如 (colstart++)。当然，在某些情况下这可能有用，但我不认为您的情况是其中之一。

使用(colstart+1)代替；它不会更改 colstart 变量本身的值，看起来这就是您真正想要做的。

更详细地说，假设 colstart 是 4:

System.out.println(colstart); // prints 4
System.out.println(colstart++); // prints 4
System.out.println(colstart); // prints 5

比较:

System.out.println(colstart); // prints 4
System.out.println(colstart+1); // prints 5
System.out.println(colstart); // prints 4