使用扫描仪从文件双精度值读取-InputMismatchException? [英] Reading from file double value using Scanner - InputMismatchException?

问题描述

我尝试从文件双精度值中读取数据，并为此目的使用了Scanner.

I tried read from file double values and using Scanner with this aim.

它抛出 InputMismatchException :

"input.txt"  java.util.InputMismatchException
    at java.util.Scanner.throwFor(Scanner.java:909)
    at java.util.Scanner.next(Scanner.java:1530)
    at java.util.Scanner.nextDouble(Scanner.java:2456)

我不明白为什么会这样?

And I can't understand why this happen?

代码:

public class Largest
{
    public static void main(String[] args)
    throws FileNotFoundException
    {
        String filename = "input.txt"; 
        Scanner in = new Scanner(filename);

        double largest = in.nextDouble();
        while (in.hasNextDouble())
        {
            double input = in.nextDouble();
            if (input > largest)
            {
                largest = input;
            }
        }
        in.close();
        System.out.println("Largest value: " + largest);
    }
}

更新:
我尝试将double largest = in.nextDouble();更改为double largest = 0;
但是输入错误:

UPDATE:
I tried change double largest = in.nextDouble(); to double largest = 0;
But it get wrong input:

filename     Actual              Expected
-------------------------------------------------------------
"input.txt"  Largest value: 0.0  Largest value: 1.343239923E9
"input2.txt" Largest value: 0.0  Largest value: 40.1   

文件内容如下:

89343455
46746846
56.78
55486411

如何解决此问题?

推荐答案

我找到了解决方案-需要创建File对象，然后将其提供给扫描程序类:

I found solution - need to create File object and then feed it to scanner class:

String filename = "input.txt"; 
File newFile = new File(filename);
Scanner in = new Scanner(newFile);

这篇关于使用扫描仪从文件双精度值读取-InputMismatchException?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！