Question

回复之前的question，我对这个问题的初步答案已经解决了，但是当它归结为循环时我遇到了另一个问题，后来通过简单地使用for循环解决了这个问题。

然而，我的问题是我不希望用户在处理异常后不断地重新启动程序，而是希望它将相同的开始问题循环给用户。我已经尝试在返回语句之后放置print语句，并尝试在try catch之后完全复制逻辑代码，但是，意识到这不会导致用户无限循环该异常。此外，在旁注上是的，我之前的问题有很好的答案，然而，没有人设法回答我的反复出现的问题，这就是为什么没有人得到他们答案的复选标记。

import java.io.*;
import java.text.DecimalFormat;

public class Test
{

    public static void main(String[] args) throws IOException
    {

        double x;
        x = circlemethods(0.0, 0.0, 0.0, 1.0);

    }

    public static double circlemethods(double volume, double surfacearea,
            double area, double radius) throws IOException
    {

        BufferedReader myInput = new BufferedReader(new InputStreamReader(System.in));

        String numInput;
        String reqInput;
        String amountStr;
        double numInt = 0;
        double num = 0;
        double answer = 0;
        double amount = 0;
        double answer2 = 0;
        double answer3 = 0;
        double answer4 = 0;

        for (double i = 0; i < 999; i++)
            ;
        try
        {

            // for (double i = 0; i < 999; i++);

            // while (numInt != 999) {

            System.out.println("This program will ask for a given user radius, then proceed to calculate the user input");
            System.out.println("The program will use four methods to achieve this, all calling back to the main method");
            System.out.println("Press any key to continue");
            numInput = myInput.readLine();

            System.out.println("First, what would you like to calculate?");
            System.out.println("Enter '1' for Circumference, '2' for area, '3' for volume, or '4' for surface area");
            reqInput = myInput.readLine();
            numInt = Double.parseDouble(reqInput);

            System.out.println("Now enter the radius of the required shape(Half of diameter)");
            numInput = myInput.readLine();
            num = Double.parseDouble(numInput);

            DecimalFormat nextAmount = new DecimalFormat("0.00");
            amountStr = nextAmount.format(amount);

            if (numInt == 1)
            {
                System.out.println("You chose to calculate circumference, given the radius :" + num);
                answer = (3.14) * (2) * (num);
                System.out.print("The circumference of that sphere is :");
                System.out.println(answer + "cm³");
                return answer;
            }
            else if (numInt == 2)
            {
                System.out.println("You chose to calculate area, given the radius :" + num);
                answer2 = (3.14) * 2;
                System.out.print("The area of the circle is :");
                System.out.println(answer2 + "cm²");
                return answer2;
            }
            else if (numInt == 3)
            {
                System.out.println("You chose to calculate volume, given the radius :" + num);
                answer3 = 4 / 3 * (3.14) * (num) * (3) * (3) * (3);
                System.out.print("The volume of that sphere is : cm³");
                System.out.println(answer3 + "cm³");
                return answer3;
            }
            else
            // if (numInt == 4)
            {
                System.out.println("You chose to calculate surface area, given the radius :" + num);
                answer4 = 4 * (3.14) * (num) * (2) * (2);
                System.out.print("The Surface area of that sphere is :");
                System.out.println(answer4 + "cm²");
                return answer4;

            }

        } catch (Exception e)
        {
            System.out.println("Please do not enter any string values, next time input enter a number ");
            return 0;
            // how to loop this untill the user inputs a number????

        }

    }

}

Answer 1

您需要循环，直到获得有效值。一种方法是循环，直到布尔值设置为true。尝试类似的东西：

boolean inputIsValid = false;
while (!inputIsValid) { ...

然后，当您确定有有效输入时，请添加以下行：

inputIsValid = true;

您的循环将继续，直到inputIsValid变为true。

你也可以创建一个无尽的while循环。然后，当您收到有效输入时，break退出循环：

while(true) {
    //when valid input is received
    break;
}

Answer 2

首先，使用while(true)循环而不是循环999次。（考虑到它后面有分号，该循环实际上并没有做任何事情。）

然后，您从return 0;阻止中移除catch。

所以它会是

while(true) {
    try {
        .... //your code
    }
catch {...}
} //while loop end bracket

这样，循环只有在到达你的一个返回语句时才会结束。

如何进行异常处理循环（无限次）

2 个答案: