Question

这是初学者的问题。我想修改计算多边形面积的程序。多边形必须至少具有3个边。如何排除错误的数据输入？（1面，0面，-4面等）

import java.util.Scanner;

    public class Polygon {

        private static Scanner input;

        public static double polygonArea(double n, double s) {
            // (n*s^2)/(4*tan(π/n))

            return (n * s * s) / (4 * Math.tan(Math.PI / n));

        }

        public static void main(String[] args) {
            input = new Scanner(System.in);
            System.out.println("Input the number of sides: ");

            double sideNumber = input.nextDouble();

            // System.out.println("Wrong number of sides!");

            System.out.println("Input the length of one of the sides: ");
            double sideLenght = input.nextDouble();

            input.close();

            System.out.println("The area of a polygon is: " + polygonArea(sideNumber, sideLenght));

        }

    }

Answer 1

尝试一下：

public class Polygon {

    private static Scanner input;

    public static double polygonArea(double n, double s) {
        // (n*s^2)/(4*tan(π/n))

        return (n * s * s) / (4 * Math.tan(Math.PI / n));

    }

    public static void main(String[] args) {
        input = new Scanner(System.in);
        double sideNumber = 0;

        while (sideNumber <= 2) {
            System.out.println("Input the number of sides: ");
            sideNumber = input.nextDouble();
        };


        // System.out.println("Wrong number of sides!");

        System.out.println("Input the length of one of the sides: ");
        double sideLenght = input.nextDouble();

        input.close();

        System.out.println("The area of a polygon is: " + polygonArea(sideNumber, sideLenght));

    }
}

当号码错误时，仍然会丢失其他消息。祝您学习愉快：）

Answer 2

您可以将输入代码包装在do-while中并循环，直到输入有效为止。

类似

input = new Scanner(System.in);
        System.out.println("Input the number of sides: ");
boolean invalidInput = true;
do {
    double sideNumber = input.nextDouble();
    if(sideNumber > 2){
       invalidInput = false;
    }else{
    System.out.println("Wrong number of sides!");
    }
}while (invalidInput)

显然，您可以对其他输入执行相同的操作，并检查该值是否为正。

Answer 3

我终于用boolean做到了，并执行while循环。谢谢。

public static void main(String[] args) {
    double sideNumber;
    input = new Scanner(System.in);
    System.out.println("Input the number of sides: ");
    boolean invalidInput = true;
    do {
        sideNumber = input.nextDouble();
        if (sideNumber > 2) {
            invalidInput = false;
        } else
            System.out.println("Wrong number of sides!");
    } while (invalidInput);


    System.out.println("Input the length of one of the sides: ");
    double sideLenght = input.nextDouble();

    input.close();

    System.out.println("The area of a polygon is: " + polygonArea(sideNumber, sideLenght));

如何排除错误的数据输入

3 个答案: