java - 返回Java代码的开头(计算器的主菜单)

我是Java的新手，对Java来说是个菜鸟，而且我正在尝试制作一个计算器，并未测试所有工具是否正常工作，但是我遇到了问题。我似乎无法弄清楚执行一次计算后如何返回主菜单。我在最后添加了该问题，以提示用户退出或继续返回主菜单。我只是不知道要在if（whatnow == Y）{中放什么，我应该怎么做才能返回主菜单？？ }。很抱歉，如果它有点长，但实际上它们都是一样的，所以就跳过计算吧。任何帮助表示赞赏。我对Java真的很陌生，可能必须重新编写这段代码。

package practice;

import java.util.Scanner;

public static void main(String[] args){

    Scanner scan = new Scanner(System.in);

    int choice;
    int firstnumber;
    int secondnumber;
    int result;
    char whatnow;

    System.out.println("Welcome to StemCalc Z Edition(Integers only)!");
    System.out.println("Made with love and basic Java");
    System.out.println("Which math operation would you like to perform?");
    System.out.println("");
    System.out.println("WARNING: Enter the integer x, press ENTER, then enter y");
    System.out.println("");
    System.out.println("[1]-Addition (+)");
    System.out.println("[2]-Subtraction (-)");
    System.out.println("[3]-Multiplication (x)");
    System.out.println("[4]-Division (/)");
    System.out.println("");
    System.out.println("Enter your choice[1-4 or 99]:"); choice = scan.nextInt();

    while ((choice < 1 || choice > 4) && choice != 99) {
        System.out.println("Please enter 1, 2, 3, 4, or 99: ");
        choice = scan.nextInt();
    }

    if (choice == 1){
        System.out.println("Enter two integer to add(x + y)");

        firstnumber = scan.nextInt();
        secondnumber = scan.nextInt();
        result = firstnumber + secondnumber;

        System.out.println(firstnumber + " + " + secondnumber + " = " + result);
    }

    else if (choice == 2) {
        System.out.println("Enter two integers to subtract(x - y)");

        firstnumber = scan.nextInt();
        secondnumber = scan.nextInt();
        result = firstnumber - secondnumber;

        System.out.println(firstnumber + " - " + secondnumber + " = " + result);
    }

    else if (choice == 3) {
        System.out.println("Enter two integers to multiply(x * y)");

        firstnumber = scan.nextInt();
        secondnumber = scan.nextInt();
        result = firstnumber * secondnumber;

        System.out.println(firstnumber + " * " + secondnumber + " = " + result);
    }

    else if (choice == 4) {
        System.out.println("Enter to integers to divide(x / y)");

        firstnumber = scan.nextInt();
        secondnumber = scan.nextInt();

        while (secondnumber == 0) {
            System.out.println("ERROR-CANNOT DIVIDE TO ZERO! Type another integer:");
            secondnumber = scan.nextInt();
        }

        result = firstnumber / secondnumber;

        System.out.println(firstnumber + " / " + secondnumber + " = " + result);
        }

    else if (choice == 99) {
        System.exit(0);

    }

    while (choice !=99) {
        System.out.println("Do you want to continue calculating? [Y/N]:"); whatnow = scan.next().charAt(0);

        if (whatnow == 'Y' || whatnow == 'y') {

        }

        if (whatnow == 'N' || whatnow == 'n') {
            System.exit(0);
        }
    }
}

}

附注：我编辑了结尾，使开头看起来像while（true）：

`while (choice !=99) {
            System.out.println("Do you want to continue calculating? [Y/N]:"); whatnow = scan.next().charAt(0);

            while(whatnow != 'Y' || whatnow != 'y' || whatnow !='N' || whatnow !='n') {
     System.out.println("Enter [Y/N] only:"); whatnow = scan.next().charAt(0);
            }

            if (whatnow == 'N' || whatnow == 'n') {
                System.exit(0);`

最佳答案

您只需要重复编写的所有内容，直到用户插入N。因此，您要做的就是将所有内容放入while(true)循环中，其最后一条指令将是：

if (whatnow == 'N' || whatnow = 'n') {
    System.exit(0);
}

这样，如果用户在N或n之外插入任何内容，循环将把他带回到主菜单打印部分，因此也许您需要以与您相同的方式对whatnow的值进行测试为choice做过。

结果将是这样的：

public static void main(String[] args){

    ...

    while(true){
        System.out.println("Welcome to StemCalc Z Edition(Integers only)!");

        ...

        while (choice !=99) {
            System.out.println("Do you want to continue calculating? [Y/N]:"); whatnow = scan.next().charAt(0);

            //insert some loop to ensure that the value of whatnow will be either Y or N

            if (whatnow == 'N' || whatnow == 'n') {
                System.exit(0);
            }
        }
    }
}

编辑

这是我对上一条评论的预期示例代码：

public static void main(String[] args){
    char whatnow = 'Y';
    Scanner scan = new Scanner(System.in);

    while (whatnow != 'N' && whatnow != 'n') {
        int choice = printMenuAndAsk(scan);

        if (choice == 99)
            break;
        else performOperation(choice, scan);

        System.out.println("Do you want to continue calculating? [Y/N]:");
        whatnow = scan.next().charAt(0);

        while(whatnow != 'N' && whatnow != 'Y' && whatnow != 'n' && whatnow != 'y') {
            System.out.println("Incorrect answer");
            whatnow = scan.next().charAt(0);
        }
    }
    scan.close();
}

public static int printMenuAndAsk(Scanner scan) {
    int choice;

    System.out.println("Welcome to StemCalc Z Edition(Integers only)!");
    ...
    System.out.println("Enter your choice[1-4 or 99]:");
    choice = scan.nextInt();

    while ((choice < 1 || choice > 4) && choice != 99) {
        System.out.println("Please enter 1, 2, 3, 4, or 99: ");
        choice = scan.nextInt();
    }

    return choice;
}

public static void performOperation(int operation, Scanner scan) {
    System.out.println("Enter first:");
    int firstnumber = scan.nextInt();
    System.out.println("Enter second:");
    int secondnumber = scan.nextInt();

    if (choice == 1)
        System.out.println(firstnumber + " + " + secondnumber + " = " + (firstnumber+secondnumber));
    else if (choice == 2)
        System.out.println(firstnumber + " - " + secondnumber + " = " + (firstnumber-secondnumber));
    else if (choice == 3)
        System.out.println(firstnumber + " * " + secondnumber + " = " + (firstnumber*secondnumber));
    else if (choice == 4) {
        while (secondnumber == 0) {
            System.out.println("ERROR-CANNOT DIVIDE TO ZERO! Type another integer:");
            secondnumber = scan.nextInt();
        }
        System.out.println(firstnumber + " / " + secondnumber + " = " + (firstnumber/secondnumber));
    }
}