java - java中toString函数的问题(使用局部变量)

Question

我在java程序中有一个类，我使用toString函数来检索数据。 toString 检查同一个类中的私有(private)函数，该函数返回一个 int 值，用于显示不同类型的返回消息。~

问题是，如果我在字符串函数中使用局部变量，结果都很好，但如果我直接检查私有(private)函数的 if 语句，则该函数不会返回任何值。

private int computerTryHorizontalPlay() {

        int repeatedMyValueCount = 0;
        int repeatedYourValueCount = 0;
        int[] myPositions = new int[3];
        int[] yourPositions = new int[3];

        for (int a = 0; a < 3; a++) {
            int repeatedMyValue = 0;
            int repeatedYourValue = 0;
            int emptyFields = 0;
            int[] emptyPosition = new int[2];
            for (int b = 0; b < 3; b++) {
                if (jogoGalo[a][b] == 'X') {
                    repeatedMyValue++;
                } else if (jogoGalo[a][b] == 'O') {
                    repeatedYourValue++;
                }
                if (jogoGalo[a][b] == '-') {
                    emptyPosition[0] = a;
                    emptyPosition[1] = b;
                    emptyFields++;
                }
            }

            if (repeatedMyValue == 3 || repeatedYourValue == 3) {
                return 3;
            } else {
                if (emptyFields == 1) {
                    if (repeatedMyValue == 2) {
                        repeatedMyValueCount++;
                        myPositions[repeatedMyValueCount - 1] = emptyPosition[0];
                        myPositions[repeatedMyValueCount] = emptyPosition[1];
                    } else if (repeatedYourValue == 2) {
                        repeatedYourValueCount++;
                        yourPositions[repeatedYourValueCount - 1] = emptyPosition[0];
                        yourPositions[repeatedYourValueCount] = emptyPosition[1];
                    }
                }
            }
        }

        if (repeatedMyValueCount > 0) {
            jogoGalo[myPositions[0]][myPositions[1]] = 'X';
            return 2;
        } else if (repeatedYourValueCount > 0) {
            jogoGalo[yourPositions[0]][yourPositions[1]] = 'X';
            return 1;
        }

        return 0;
    }

这行不通!

    public String toString() {
        if(computerTryHorizontalPlay() == 3) {
            return "The game has already ended!";
        }
        else if(computerTryHorizontalPlay() == 2) {
            return "Computer won!";
        }
        else if(computerTryHorizontalPlay() == 1) {
            return "Computer defendeu!";
        }
        return null;
    }

这有效!

public String toString() {

        int horizontalFunctionValue = computerTryHorizontalPlay();

        if(horizontalFunctionValue == 3) {
            return "The game has already ended!";
        }
        else if(horizontalFunctionValue == 2) {
            return "Computer won!";
        }
        else if(horizontalFunctionValue == 1) {
            return "Computer defendeu!";
        }
        return null;
    }
}

Answer 1

toString() 必须是只读方法，即不允许有诸如更改对象状态之类的副作用。由于 computerTryHorizo​​ntalPlay() 是一个状态更改方法，因此不允许您从 toString() 调用它。

由于唯一的状态更改发生在最后一个 if 语句中，因此您可以更改代码，以便在从 toString() 调用时不执行播放，如下所示:

private int computerTryHorizontalPlay() {
    return computerTryHorizontalPlay(true);
}

private int computerTryHorizontalPlay(boolean doMove) {

    // lots of code here

    if (repeatedMyValueCount > 0) {
        if (doMove)
            jogoGalo[myPositions[0]][myPositions[1]] = 'X';
        return 2;
    } else if (repeatedYourValueCount > 0) {
        if (doMove)
            jogoGalo[yourPositions[0]][yourPositions[1]] = 'X';
        return 1;
    }

    return 0;
}

public String toString() {
    if(computerTryHorizontalPlay(false) == 3) {
        return "The game has already ended!";
    }
    else if(computerTryHorizontalPlay(false) == 2) {
        return "Computer won!";
    }
    else if(computerTryHorizontalPlay(false) == 1) {
        return "Computer defeated!";
    }
    return null;
}