Question

我是新手，有点像Java的菜鸟，我试图制作一个计算器，没有测试一切，看它是否有效，但我遇到了问题。我似乎无法弄清楚如何在执行一次计算后返回主菜单。我最后添加了这个问题，以提示用户退出或继续返回主菜单。我只是不知道在if（whatnow == Y）中放入什么{wtf我应该回到主菜单？ }。对不起，如果它有点长或什么的，但他们真的都是一样的，所以只是跳过计算的东西。任何帮助赞赏。我是java的新手，我可能不得不再次编写这段代码。

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);
        }
    }
}

}

P.S：我在开头编辑了结尾看起来像这样的东西（真实）：

`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);`

Answer 1

在用户插入N之前，您只需要重复所写的所有内容。所以你要做的就是将所有内容放在while(true)循环中，其最后一条指令是：

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，循环会将他带回主菜单打印部分，因此您可能需要在{的值上添加测试{1}}与您对whatnow的处理方式相同。

结果如下：

choice

修改

以下是我对上次评论的预期示例代码：

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); } } } }

Answer 2

尝试将整个代码放在while(true)块中，而不是尝试在最后放置while循环。最后使用if语句，您可以询问用户是否想要继续使用。使用break关键字退出循环。尝试像这样退出：

if(input == 'n'){break;}

这样做是因为它退出了while循环。您可以在while块之外执行更多指令。

Answer 3

您可以按如下方式更改：

您的主要方法如下：

public static void main(String[] args) {
        calc();
    }

然后创建一个名为calc()的方法：

public static void calc() {

        Scanner scan = new Scanner(System.in);

        //the rest of your code

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

        }

        calc(); //call the method again at the end of your code
                //remove your while loop

    }

返回Java代码的开头（计算器的主菜单）

3 个答案: