如何让循环停止

I am trying to stop a loop for my calculator program, but I am not allowed to use breaks or system.exit. How would I go so with stopping my loop my just putting in 5 for the menu? Also How do I make the program quit if I would put in "n" for the question asking would I like to use the calculator again? P.S. I am using Java.

我试图阻止我的计算器程序循环,但我不允许使用break或system.exit。如何停止我的循环我只需要输入5个菜单?另外,如果我在问题中输入“n”,那么如何让程序退出?我想再次使用计算器吗?附:我正在使用Java。

public static void main (String args []) {
    String MainMenu = " Calculator Options \n\n1. Addition\n2" +
            " Subtraction\n3. Multiplication\n4. Division\n5. Exit";
    menu (MainMenu);

    while (true) {
       String YesorNo = JOptionPane.showInputDialog("Would You Like to Use the Calculator Again (y / n)? ");

       if (YesorNo.equals ("y")) {
           menu (MainMenu);
       }

       if (YesorNo.equals ("n")) {

       }
    }
}

public static int menu (String info) {
    String choice = JOptionPane.showInputDialog (info);
    if (choice.equals ("1"))
        return Addition();
    else if (choice.equals ("2"))
        return Subtraction();
    else if (choice.equals ("3"))
        return  Multiplication();
    else if (choice.equals ("4"))
        return  Division();
    else
        return 0;
}

2 个解决方案

#1

Use the break keyword.

使用break关键字。

if (YesorNo.equals ("n")) {
    break;
}

Or place the condition in the while-loop and use the keyword do.

或者将条件放在while循环中并使用关键字do。

do {
    // code & blaaa .. blaaa & code
} while (YesorNo.equals("y"));

#2

To answer both of you questions:

回答你们两个问题:

You simply need to use a do-while loop and include both conditions in there. But With your current implementation that wont be working 100% of the time.

您只需要使用do-while循环并在其中包含两个条件。但是,您目前的实施不会100%的时间都在工作。

Reason beeing, you return the action aswell as the result from menu.

理由是,您返回动作以及菜单的结果。

To start of, that´s how your loop could look like.

首先,这是你的循环的样子。

do {
   String YesorNo = JOptionPane.showInputDialog ("Would You Like to Use the Calculator Again (y / n)? ");
   int menuReturn = menu (MainMenu);
} while (YesorNo.equals("y") || menuReturn != 0);

That´s what could work, the menu method does return 0 if it is not inside the values 0-4. But what happens when the result of any of your mathemematical operations is 0? You would also close the calculator. At this point you might want to change what menu does.

这就是可行的,如果菜单方法不在值0-4内,则返回0。但是当你的任何数学运算的结果为0时会发生什么?你也可以关闭计算器。此时您可能想要更改菜单的功能。

private static int result = 0;

public static int menu (String info) {
   String choice = JOptionPane.showInputDialog (info);
   if (choice.equals ("1")) {
       result = Addition();
       return 1;
   }
   else if (choice.equals ("2")) {
       result = Subtraction();
       return 1;
   }
   else if (choice.equals ("3")) {
       result = Multiplication();
       return  1;
   }  
   else if (choice.equals ("4")) {
       result = Division();
       return 1;
   }
   else if (choice.equals("5"))
       return -1;
   else 
       return 0;

your loop design would change now to something like the following.

你的循环设计现在会改变为类似下面的东西。

do {
   String YesorNo = JOptionPane.showInputDialog ("Would You Like to Use the Calculator Again (y / n)? ");
   int menuReturn = menu (MainMenu);
   // Work with the result now
   if (menuReturn == 0) // invalid input;
} while (YesorNo.equals("y") || menuReturn != -1);

But in order to make it fully contract the OOP principle you might have to rewrite a little bit more code then shown in the answer.

但是为了使其完全符合OOP原则,您可能需要重写一些代码,然后在答案中显示。

#1