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对上一个问题的回应，我对该问题的最初答案已经解决，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。

但是，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，而是希望它向用户循环相同的开始问题。我尝试在 return 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，我意识到这不会导致用户无限次循环异常。另外，顺便说一句，是的，我之前的问题有很好的答案，但是，没有人能回答我更反复出现的问题，这就是为什么没有人对他们的答案打勾的原因。

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????

        }

    }

}
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2 回答 2

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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真。尝试类似的事情：

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

然后，当您确定您有一个有效的输入时，添加以下行：

inputIsValid = true;

您的循环将继续，直到 inputIsValid 变为真。

您还可以创建一个无休止的 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;
}
于 2013-03-18T23:56:38.467 回答
0

首先，您使用while(true)循环而不是循环 999 次。（考虑到它后面有一个分号，这个循环实际上并没有做任何事情。）

然后，您return 0;从catch块中删除 。

所以它会是

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

这样，循环只有在到达您的返回语句之一时才会结束。

于 2013-03-19T00:00:10.427 回答