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java - 如何排除错误的数据输入

问题描述

这是一个初学者的问题。我想修改计算多边形面积的程序。多边形必须至少有 3 条边。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));

        }

    }

标签： javajava.util.scanner

解决方案

我终于用布尔值做了它并做while循环。谢谢帮助。

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));

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