Question

我正在进行Connect Four游戏练习。除错误检查外，一切正常。用户输入一个字符串，我需要首先检查它是否是正确的长度和格式（嵌套while循环），然后如果条目创建一个赢家来结束游戏（顶部while循环）。

但是，即使该条目无效，并且嵌套的while循环仍应循环，Java也会在外部while循环中执行其余代码。我在这里做错了什么？

while (true) {
    // get row and column from user
    int row=1, column=1;
    boolean validr = false, validc = false;
    do {
        System.out.print("Type the row and column you would like to drop your chip, separated by a space: ");
        String drop = keyboard.nextLine();

        // check that input is proper length
        if(drop.length() == 3 && drop.contains(" ")) {
            int space = drop.indexOf(" ");

            // check if row is integer
            try { 
                int testrow = Integer.parseInt(drop.substring(0, space));
                //check if between 1 and 6
                if (testrow > 0 && testrow < 7) {
                    row = Integer.parseInt(drop.substring(0, space));
                    validr = true;
                } else {
                    System.out.println("Whoops, that row isn't valid!");
                }
            } catch (NumberFormatException ex) {
                System.out.println("Make sure you're typing valid row and column numbers!");
            }

            // check if column is valid
            try {
                int testcolumn = Integer.parseInt(drop.substring(space+1));
                //check if between 1 and 7
                if (testcolumn > 0 && testcolumn < 8) {
                    column = Integer.parseInt(drop.substring(space+1));
                    validc = true;
                } else {
                    System.out.println("Whoops, that column isn't valid!");
                }
            } catch (NumberFormatException ex) {
                System.out.println("Make sure you're typing valid row and column numbers!");
            }
        } else {
            System.out.println("Remember, type the row number, followed by a space, and then the column number.");
        }
    } while (!validr && !validc);

    // change selected array value to 'x'
    board[row-1][column-1] = "x";

    // check if there is now a winner

    if (checkBoard(board) == true) {
        printBoard(board);
        System.out.println("Congratulations!  You got four in a row!");
        break;
    }
    else {
        printBoard(board);
    }
}

它会显示抛出的任何异常的错误消息，但它也会将board[1][1]更改为＆＃34; x＆＃34;并从这里粘贴的整个代码的顶部重新开始，而不仅仅是嵌套的while循环的顶部。

Answer 1

您

 while (!validr && !validc);

条件意味着只要validr和validc都为假（即行号和列号都无效），内循环就会继续。

您需要validr和validc才能退出内循环，因此您的条件应为：

while (!validr || !validc);

即。只要validr或validc为假，循环就会继续。

Answer 2

！（a＆amp; b）=！a || ！b “not（A和B）”与“（不是A）或（不是B）”

相同

Demorgan的法律。在你的程序中应用这个你的while循环应该是

while (!validr || !validc);

在嵌套循环完成之前嵌套while循环执行顶循环 - Java

2 个答案: