我如何解决这个无限的 while 循环

Question

我正在使这个程序能够计算阶乘。 如果他们输入的值超过 20，我需要它说一句话，但我已经创建了无限循环。 我的台词说

System.out.print ("ERROR: The result is inaccurate because the number was    too large for the data type");}

是一个无限循环。 我似乎无法弄清楚如何解决它。 我试过移动东西的位置，但我无法弄清楚。 任何帮助表示赞赏。

import java.util.Scanner;
import java.text.NumberFormat;

public class FactoralApp
{
public static void main(String[] arge)
{

    //Welcome users the the application and get user input
    System.out.print("Welcome to the Factoral Calculator" + "\n");


    int num;

    Scanner sc = new Scanner(System.in);
    String choice = "y";
    while (choice.equalsIgnoreCase("y")) {  //set up the while loop so that users can find many factorials

    long factorial=1; //initialize variables


    System.out.print("\n" + "Enter an integer between 1 and 20: "); //promt users for input
    num = sc.nextInt();

    for (int i = num; i >= 1; i--){  //Calculate factorial
    factorial = factorial * i;}

    while (num > 20) {
        System.out.print ("ERROR: The result is inaccurate because the number was too large for the data type");}




    // Format and display the results

    NumberFormat number = NumberFormat.getNumberInstance();

    String message =
                ("\n" + "The factoral of " + num + " is " + number.format(factorial) + "." + "\n"); //create message

    System.out.println(message);  // Output the formated message

    System.out.print ("Continue (y/n): "); //promt users for input
    choice = sc.next();
    } // End While



} // End main ()



} // End Class

Answer 1

我认为不是 while，您需要一个 if 条件来检查输入的数字是否大于 20。

if(num > 20) {  //the result cannot be stored in a long data type so alert
        System.out.print ("ERROR: The result is inaccurate because the number was too large for the data type");}

// Format and display the results

NumberFormat number = NumberFormat.getNumberInstance();

String message =
            ("\n" + "The factorial of " + num + " is " + number.format(factorial) + "." + "\n"); //create message

System.out.println(message);  // Output the formatted message

System.out.print ("Continue (y/n): "); //prompt users for input
choice = sc.next();
} // End if

Answer 2

我建议您了解控制语句的工作原理。 while是一个循环，显然它会一直运行直到条件满足。 下面是正确的代码。

public static void main(String[] args) { //Welcome users the the application and get user input
        System.out.print("Welcome to the Factoral Calculator" + "\n");


        int num;

        Scanner sc = new Scanner(System.in);
        String choice = "y";
        while (choice.equalsIgnoreCase("y")) {  //set up the while loop so that users can find many factorials

        long factorial=1; //initialize variables


        System.out.print("\n" + "Enter an integer between 1 and 20: "); //promt users for input
        num = sc.nextInt();

        for (int i = num; i >= 1; i--){  //Calculate factorial
        factorial = factorial * i;}

        if (num > 20) {
            System.out.print ("ERROR: The result is inaccurate because the number was too large for the data type");}




        // Format and display the results

        NumberFormat number = NumberFormat.getNumberInstance();

        String message =
                    ("\n" + "The factoral of " + num + " is " + number.format(factorial) + "." + "\n"); //create message

        System.out.println(message);  // Output the formated message

        System.out.print ("Continue (y/n): "); //promt users for input
        choice = sc.next();
        } // End While



}

说明-：仅更新了以下部分代码。 现在上面的代码将打印ERROR: The result is inaccurate because the number was too large for the data type error 只有一次。

 if (num > 20) {
            System.out.print ("ERROR: The result is inaccurate because the number was too large for the data type");}   

如果此代码更改不符合您的要求，请提供更多详细信息。 您想打印该错误消息多少次。

Answer 3

您永远不会在 while 循环中更改num变量的值。 由于这是您在 while 循环的布尔条件中检查的变量，因此条件永远不会改变，并且 while 循环有永远运行的风险。

解决方案：更新循环内的变量。 使用您的 Scanner 变量 sc，就像您在循环之前所做的那样。