java - 使用循环进行输入验证和异常处理

Question

如何使用循环进行输入验证以及 try 和 catch block 来捕获输入不匹配异常？

这是我的主要方法

import java.util.InputMismatchException;
import java.util.Scanner;

public class labBookFortyThree {
    public static void main(String[] args) {
        Scanner myInput = new Scanner(System.in);
        double circle, rect1, rect2, cyl1, cyl2;
        int input = 0;
        System.out.println("Press 1 to calc circle, 2 for rect, 3 for cyln");

        try {
            input = myInput.nextInt();
        } catch (InputMismatchException e) {
            System.out.println("Please enter a proper value");
        }

        if (input == 1) {
            System.out.println("enter radius");
            circle = myInput.nextDouble();
            System.out.println("area of circle is " + areas.area(circle));
        } else if (input == 2) {
            System.out.println("enter length and height");
            rect1 = myInput.nextDouble();
            rect2 = myInput.nextDouble();
            System.out.println("area of rect is " + areas.area(rect1, rect2));
        } else if (input == 3) {
            System.out.println("enter rad, height");
            cyl1 = myInput.nextDouble();
            cyl2 = myInput.nextDouble();
            int useless = 0;
            System.out.println("Area of cyl is " + areas.area(cyl1, cyl2, useless));
        }
    }
}

这是我的类区域

public class areas {
    public static double area(double rad) {
        double area = 3.14 * (rad * rad);
        return area;
    }

    public static double area(double width, double height) {
        double area = width * height;
        return area;
    }

    public static double area(double rad, double height, int useless) {
        double area = (3.14 * (rad * rad) * height);
        return area;
    }
}

我应该在哪里放置输入验证循环？有没有更好的办法？我可以在 catch 或 try block 中创造性地做些什么？

Answer 1

而不是

try {
  input = myInput.nextInt();
} catch (InputMismatchException e) {
  System.out.println("Please enter a proper value");
}

一种可能的方法是使用循环并检查您期望的输入，例如 1 到 3 之间的 int，

int input = 0;
while(input < 1 || input > 3) {
  if (myInput.hasNextInt()) {
    input = myInput.nextInt();
  } else if (myInput.hasNext()) {
    System.out.println("Please enter a proper value");
    myInput.next();
  } else {
    System.err.println("No more input");
    System.exit(1);
  }
}
// input is 1,2 or 3. Or the program ended.