Question

我必须在java中创建一个简单的计算器来调用方法，而不是一遍又一遍地重复整个程序。我的所有方法都有效，它允许用户根据需要做出错误的选择，直到做出正确的选择。我遇到的问题是，在操作完成并得出答案后，它不会突破案例。

package menuDrivenCalculator;

import java.util.Scanner;

public class MenuDrivenCalculator {
static Scanner input = new Scanner(System.in);

public static void main(String[] args) {
    // TODO Auto-generated method stub

        int menuOption = getMenuOption();

        while (menuOption < 1 || menuOption > 6) {
            System.out.println("I'm sorry, " + menuOption + " is not a valid choice. Please try again.");
            menuOption = getMenuOption();
            if (menuOption >= 1 && menuOption <= 6) {
                break;
            }
        }

        while (menuOption >= 1 && menuOption <= 6) {

            switch (menuOption) {
            case 1:

                System.out.print("What is the first number? ");
                double operand1 = getOperand();
                System.out.print("What is the second number?");
                double operand2 = getOperand();

                double add = add(operand1, operand2);
                System.out.println("Your answer is: " + add);

                break;

            case 2:

                System.out.print("What is the first number? ");
                operand1 = getOperand();
                System.out.print("What is the second number?");
                operand2 = getOperand();

                double subtract = subtract(operand1, operand2);
                System.out.println("Your answer is: " + subtract);

                break;

            case 3:

                System.out.print("What is the first number? ");
                operand1 = getOperand();
                System.out.print("What is the second number?");
                operand2 = getOperand();

                double multiply = multiply(operand1, operand2);
                System.out.println("Your answer is: " + multiply);
                break;

            case 4:

                System.out.print("What is the first number? ");
                operand1 = getOperand();
                System.out.print("What is the second number?");
                operand2 = getOperand();

                double divide = divide(operand1, operand2);
                System.out.println("Your answer is: " + divide);

                break;

            case 5:

                System.out.print("What is the lower limit? ");
                operand1 = getOperand();
                System.out.print("What is the upper limit?");
                operand2 = getOperand();

                double random = random(operand1, operand2);
                System.out.println("Your answer is: " + random);

                break;

            case 6:
                System.out.println("Goodbye!");
                return;

            }

        }
}

public static int getMenuOption() {

    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? ");
    int menuOption = input.nextInt();

    return menuOption;
}

public static double getOperand() {

    double operand = input.nextDouble();

    return operand;
}

public static double add(double operand1, double operand2) {

    double add = (operand1 + operand2);

    return add;
}

public static double subtract(double operand1, double operand2) {

    double subtract = (operand1 - operand2);

    return subtract;
}

public static double multiply(double operand1, double operand2) {

    double multiply = (operand1 * operand2);

    return multiply;
}

public static double divide(double operand1, double operand2) {

    double divide = 0;
    if (operand2 == 0) {
        divide = Double.NaN;
    } else if (operand2 != 0) {
        divide = (operand1 / operand2);
    }
    return divide;
}

public static double random(double operand1, double operand2) {

    double random = Math.random() * operand2 + operand1;

    return random;
}
}

正在发生的事情是程序会一次又一次地提示用户输入相同的操作，直到您手动停止程序运行。我尝试将整个东西放在不同类型的循环中，没有任何改变。

Answer 1

由于执行操作的代码位于循环（while (menuOption >= 1 && menuOption <= 6)）内，程序将继续循环上次选择的操作。

您需要一个包含getMenuOption()方法的循环，以便用户可以选择其他操作。

为了做到这一点，你可以只用1来处理所有事情（请记住你也可以使用default内的switch案例），而不是有2个单独的循环。

由于它似乎是家庭作业，我不会给你完整的解决方案，但如果你有其他具体的疑问，请告诉我们。

Answer 2

如果你不想重复，为什么把switch语句放在while循环中？将“while”替换为代码中的“if”

如何打破案例并重复程序，直到用户选择退出

2 个答案: