如何从方法中提取整数？

Question

我必须使用方法public static int getMenuOption，我无法让它返回一个整数。

它必须按照我的方式循环，如果选择正确或连续3次错误则重复循环，您将退出。

我无法理解如何将 intValue 拉出循环？

public static int getMenuOption() {
    Scanner theScanner = new Scanner(System.in);
    for (int i = 0; i < 3; i++) {
        int intValue = 1;
        while (intValue > 0 && intValue < 6) {
            System.out.println("Menu");
            System.out.println("1. Add");
            System.out.println("2. Subtract");
            System.out.println("3. Multiply");
            System.out.println("4. Divide");
            System.out.println("5. Generate a random number");
            System.out.println("6. Quit\n");
            System.out.print("What would you like to do? ");
            intValue = theScanner.nextInt();
            if (intValue > 6 || intValue < 1) {
                System.out.println("I'm sorry, " + intValue +
                    " wasn't one of the options");
            }

        }
    }

    return intValue;
}

Answer 1

看起来你的 while 条件是错误的。

应该是：

while(intValue <=0 || intValue >6)

因为您希望保持在循环中，直到获得有效输入（1 到 6 之间）。

此外，尚不清楚外部 for 循环的用途。您可能应该删除它，因为在 while 循环找到有效输入后，该方法应该返回。

public static int getMenuOption() {
    Scanner theScanner = new Scanner(System.in);
    int intValue = 1;
    while (intValue <= 0 || intValue > 6) {
        System.out.println("Menu");
        System.out.println("1. Add");
        System.out.println("2. Subtract");
        System.out.println("3. Multiply");
        System.out.println("4. Divide");
        System.out.println("5. Generate a random number");
        System.out.println("6. Quit\n");
        System.out.print("What would you like to do? ");
        intValue = theScanner.nextInt();
        if (intValue > 6 || intValue < 1) {
            System.out.println("I'm sorry, " + intValue +
                " wasn't one of the options");
        }

    }

    return intValue;
}

Answer 2

你的条件不对。

制作它： while(intValue <= 0 || intValue > 6)

也可以像这样在 for 循环之外声明 intValue：

Scanner theScanner = new Scanner(System.in);
int intValue;
for (int i = 0; i < 3; i++) {
    intValue = 1;

这样做之后你应该没事了。

编辑：

public static int getMenuOption() {
    Scanner theScanner = new Scanner(System.in);
    int intValue = 1;
    for (int i = 0; i < 3; i++) { //Useless for loop.
        intValue = 1; //reset var each time
        while (intValue <= 0 || intValue > 6) {
            System.out.println("Menu");
            System.out.println("1. Add");
            System.out.println("2. Subtract");
            System.out.println("3. Multiply");
            System.out.println("4. Divide");
            System.out.println("5. Generate a random number");
            System.out.println("6. Quit\n");
            System.out.print("What would you like to do? ");
            intValue = theScanner.nextInt();
            if (intValue > 6 || intValue < 1) {
                System.out.println("I'm sorry, " + intValue +
                    " wasn't one of the options");
            } else {
                return intValue;
            }

        }
    }

    return intValue;
}

我相信这是您想要的代码：

编辑：

public static int getMenuOption() {
    Scanner theScanner = new Scanner(System.in);
    int count = 0;
    int intValue = 1;
        while (intValue <= 0 || intValue > 6) {
            System.out.println("Menu");
            System.out.println("1. Add");
            System.out.println("2. Subtract");
            System.out.println("3. Multiply");
            System.out.println("4. Divide");
            System.out.println("5. Generate a random number");
            System.out.println("6. Quit\n");
            System.out.print("What would you like to do? ");
            intValue = theScanner.nextInt();
            if (intValue > 6 || intValue < 1) {
                System.out.println("I'm sorry, " + intValue +
                    " wasn't one of the options");
                count++;
            } else if (count == 3 || intValue <= 6 && intValue >= 1) {
                return intValue;
            }

    return intValue;
}