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首先，我想说的是，在 Java 方面我是一个完整的初学者。到目前为止，我所知道的是我从大学的软件开发课程中学到的东西。我自己一直在搞砸它，我设法创建了一个应用程序，它以两个双精度值作为输入并计算用户的 BMI（体重指数）。

该程序运行良好，并且完全符合我的要求，但是，如果用户没有输入任何内容并按下回车键，则会引发异常。如果用户输入的不是数字，则会引发异常。当抛出异常时，程序停止。我想阻止这些异常完全停止程序，而是将用户返回到输入阶段并显示错误消息。

我知道它是如何完成的。有些人建议使用 try {..} catch (..) {..} 结构，我已经尝试过，但我总是设法破坏程序。

有人有想法么？

所以，这是我到目前为止的代码，如果有任何问题，我很抱歉，我已经尝试添加注释以使其更容易。

import java.io.*;

public class bmi {

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

        /**
         * User input of weight and height.
         */

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

        System.out.println("Please enter how much you weigh in KG.");
        double weight = Double.parseDouble(in.readLine()); //take weight input as double

        System.out.println("Please enter how tall you are in meters.");
        double height = Double.parseDouble(in.readLine()); //take height input as double

        /**
         * BMI calculation
         */

        double bmi = weight / Math.pow(height,2); // weight divided by height squared

        /**
         * if else statements to find if person is underweight, at a healthy weight or overweight.
         */

        if (bmi<18.5) { //if BMI is smaller than 18.5
            System.out.println("Your BMI is " + bmi + ", you are underweight.");
        }

        else if (bmi>=18.5 && bmi<=25) { //if BMI is bigger than or equal to 18.5 and smaller than or equal to 25
            System.out.println("Your BMI is " + bmi + ", you are at a healthy weight.");
        }

        else if (bmi>25) { //if bmi is bigger than 25
            System.out.println("Your BMI is " + bmi + ", you are overweight");
        }

    }

}

谢谢。

4

2 回答 2

2

代替

System.out.println("Please enter how much you weigh in KG.");
double weight = Double.parseDouble(in.readLine()); //take weight input as double

System.out.println("Please enter how tall you are in meters.");
double height = Double.parseDouble(in.readLine()); //take height input as double

使用这样的构造：

double weight = 0, height = 0;
boolean incorrectInput = true;

while(incorrectInput){
    try{
        System.out.println("Please enter how much you weigh in KG.");
        weight = Double.parseDouble(in.readLine()); //take weight input as double

        System.out.println("Please enter how tall you are in meters.");
        height = Double.parseDouble(in.readLine()); //take height input as double
        incorrectInput = false;
    }catch(NumberFormatException nxe){
        System.out.println("Incorrect value for weight or height provided. Please try again")
    }
}

您实际上在做的事情如下：

  • 声明一个布尔变量，用于控制是否要求用户输入信息。请注意，这需要在初始时间为真，直到用户输入正确的体重和身高值

  • 如果输入不符合预期，则 parseDouble() 方法会抛出 NumberFormatException。您需要捕获此输入并告诉用户该输入不是预期的。这进入你的 catch 块。解析部分进入 try 块内部。

  • 假设用户输入了预期的输入，您需要做的是设置布尔变量，以便 while 循环终止。

注意：另一种选择是使用扫描仪。您可以在 Java 教程：扫描中阅读有关其用法的更多信息

于 2012-10-28T08:36:59.190 回答
1

You can use Scanner for that. Scanner provides various methods to check appropriate types so you can use them. And there is no need to catch exceptions like NumberFormatException

    Scanner scanner = new Scanner(System.in);
    double weight = 0;
    double height = 0;
    System.out.println("Please enter how much you weigh in KG.");
    while (scanner.hasNext()) {
        if (scanner.hasNextDouble()) {
            // correct value
            weight = scanner.nextDouble();
        } else {
            System.out.println("Please enter correct value.");
            scanner.next();
            continue;
        }
        System.out.println("Please enter how tall you are in meters.");
        if (scanner.hasNextDouble()) {
            // correct value
            height = scanner.nextDouble();
        } else {
            System.out.println("Please enter correct value.");
            scanner.next();
            continue;
        }
        break;
    }
    double bmi = weight / Math.pow(height, 2);
    System.out.println("Your BMI :"+bmi);
    //Rest of the code remains the same
于 2012-10-28T08:38:03.070 回答