java - 如果输入有效，如何处理读取三角形三边并计算面积的家庭作业程序？

Question

这是我的任务:

Create a class named MyTriangle that contains the following two methods:

/** Return true if the sum of any two sides is * greater than the third side. */
public static boolean isValid (double side1, double side2, double side3)

/** Return the area of the triangle. */ 
public static double area (double side1, double side2, double side3)

Write a test program that reads three sides for a triangle and computes the area if the input is valid. Otherwise, it displays that the input is invalid.

下面的尝试: 问题:我无法弄清楚这一点，不断重读这一章并没有突破任何障碍。 问题在以下代码中进行了评论:

import java.util.Scanner;

public class NewClass1 {   

double area;
double side1, side2, side3;
double x1, x2, x3, y1, y2, y3;

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

        System.out.print("Enter two integers for side 1:");
        double x1 = input.nextDouble();
        double y1 = input.nextDouble();

        System.out.print("Enter two integers for side 2:");
        double x2 = input.nextDouble();
        double y2 = input.nextDouble();

        System.out.print("Enter two integers for side 3:");
        double x3 = input.nextDouble();
        double y3 = input.nextDouble();

        boolean isValid = true;

            if (isValid) {
                System.out.println("Input is invalid");
            }
                else
                    area(side1, side2, side3); //Using area does not work and I don't know how to remedy this. I've read the chapter over and over... I cannot get it to work.

    }

    public static double area(double side1, double side2, double side3) {
        double x1 = 0;
        double x2 = 0;
        double y1 = 0;
        double y2 = 0;
        double x3 = 0;
        double y3 = 0; 

            side1 = Math.pow(Math.pow(x2 - x1, 2) + Math.pow(y2 - y1, 2), 0.5);
            side2 = Math.pow(Math.pow(x3 - x1, 2) + Math.pow(y3 - y1, 2), 0.5);
            side3 = Math.pow(Math.pow(x3 - x2, 2) + Math.pow(y3 - y2, 2), 0.5);

            //Calculates the sides/angles using Heron's formula
            double s = (side1 + side2 + side3)/2;
            double area = Math.pow(s * (s - side1) * (s - side2) * (s - side3), 0.5);

            return (area);
    } 

    public static boolean isValid(double side1, double side2, double side3) {

        return (((side1 + side2) > side3) && ((side1 + side3) > side2) && ((side2 + side3) > side1));
    }
}

查看代码，有人可以解释我做错了什么，并解释可能的补救措施。一切都在那里，我就是无法连接点。

修订--代码

import java.util.Scanner;

public class NewClass1 {   

    public static void main(String[] args) {

            Scanner input = new Scanner(System.in);

            System.out.print("Enter side 1: ");
            double side1 = input.nextDouble();

            System.out.print("Enter side 2: ");
            double side2 = input.nextDouble();

            System.out.print("Enter side 3: ");
            double side3 = input.nextDouble();

            double a = area(side1, side2, side3);
            boolean isV = isValid(side1, side2, side3);

                    if (isV)
                        System.out.println("Inout is Invalid");
                    else
                        System.out.println("Area is: " + a);
        }

    public static boolean isValid(double side1, double side2, double side3) {

         return (((side1 + side2) > side3) && ((side1 + side3) > side2) && ((side2 + side3) > side1));
    }

    public static double area(double side1, double side2, double side3) {

                //Calculates the sides/angles using Heron's formula
        double s = (side1 + side2 + side3)/2;
        double theArea = Math.pow(s * (s - side1) * (s - side2) * (s - side3), 0.5);

            return (theArea);
    } 
}

我不断收到 NaN 作为该区域的答案。我做错了什么？

Answer 1

所以你写下: 如果输入有效，则显示错误消息。否则(else)计算区域。 你应该只交换你的 if 和 else 部分!如果您使用有效三角形的点调用它，您的程序永远不会调用 area() 方法。 此外，您永远不会调用 isValid() 方法。您将 true 赋值给变量，然后在下一行检查它，但实际检查它的方法从未被调用。

您还需要 isValid() 的辅助变量，但您只能在 area() 方法中计算它们。你应该在得到分数后立即计算它们。