java - 我完美运行的 Java 代码在 IntelliJ IDEA 中抛出异常

Question

我一直在使用 eclipse 和 OnlineGDB 来完成我的 Java 工作。我最近开始使用 IntelliJ IDEA，我非常喜欢它。但我尝试在 IntelliJ IDEA 中完成一个关于文件操作的简单项目。但它在运行过程中给我一个错误。 使用完全相同的代码，我在 OnlineGDB 中没有遇到任何问题。

import java.util.InputMismatchException;
import java.util.Scanner;
import java.io.File;
import java.io.PrintWriter;

public class Main

{
    static void createFile() throws Exception
    {
        PrintWriter output = new PrintWriter(new File("input.txt"));
        output.print("2.5");
        output.close();
    }


public static void main(String[] args) throws Exception
{
    Scanner input = new Scanner(System.in);
    Circle[] circles = new Circle[3];

    circles[0] = new Circle(1.0);

    System.out.print("Radius of the second circle => ");
    circles[1] = new Circle(input.nextFloat());
    input.close();

    createFile();
    input = new Scanner(new File("input.txt"));
    circles[2] = new Circle(input.nextFloat());
    input.close();

    for (int i = 0; i<=circles.length-1; i++)
    {
        System.out.println( "c(" + i + ") radius = " + circles[i].getRadius()
        + " area = " + circles[i].area() );
    }

    float total = 0;
    for (int i = 0; i<3; i++)
    {
        total +=circles[i].getRadius();
    }
    System.out.println("Total radius of the circles = " + total );

    total = 0;
    for (int i = 0; i<3; i++)
    {
        total+= circles[i].area();
    }
    System.out.println("Total area of the circles = " + total);
}
}

<小时/>

    public class Circle
{
    private double radius;

    public Circle (double radius)
    {
        this.radius = radius;
    }

    public double getRadius()
    {
        return radius;
    }

    public double area()
    {
        return(Math.PI * radius * radius);
    }
}

<小时/>

在这些行中它给了我“java.util.InputMismatchException”错误:

System.out.print("Radius of the second circle => ");
        circles[1] = new Circle(input.nextFloat());
        input.close();

Answer 1

System.out.print("Radius of the second circle => ");
circles[1] = new Circle(input.nextFloat());
input.close();

我将 input.nextInt() 更改为 input.nextFloat()更改期望整数读取 float (或 double ，如果您愿意)的代码部分。您应该能够输入 2.5 这样的值并且不会出现任何错误。

我在评论中解释了为什么输入 2.5 会出错

示例输出:

Radius of the second circle => 2.5
c(0) radius = 1.0 area = 3.141592653589793
c(1) radius = 2.5 area = 19.634954084936208
c(2) radius = 2.5 area = 19.634954084936208
Total radius of the circles = 6.0
Total area of the circles = 42.4115