双接受逗号而不是点 [英] Double accepted with comma instead of dot

问题描述

我无法从我的 bash 终端在我的程序中输入双精度值.下面是我用来弄清楚为什么会发生这种情况的代码.

I am unable to enter doubles value in my program from my bash terminal. Below is the code I used to figure out why it is happening.

这是我的测试代码:

import java.util.*;
public class DoubleTest {
    public static void main (String[] args) {
        Scanner sc = new Scanner(System.in);

        double n = sc.nextDouble();
        System.out.println(n);
    } 
}

使用以下输入 5，我得到了预期的结果.

With the following input 5, I get the expected results.

user $ java DoubleTest
   5
   5.0

现在是有趣的部分.我输入了一个在代码中声明的 Double，然后发生了这种情况:

Now to the interesting part. I input a Double as declared in the code, and this happens:

user $ java DoubleTest
5.0
Exception in thread "main" java.util.InputMismatchException
at java.base/java.util.Scanner.throwFor(Scanner.java:939)
at java.base/java.util.Scanner.next(Scanner.java:1594)
at java.base/java.util.Scanner.nextDouble(Scanner.java:2564)
at DoubleTest.main(DoubleTest.java:6)

当值为 5,0 时 - 结果如下:

And when giving a value of 5,0 - this is the result:

user $ java DoubleTest
5,0
5.0

所以看起来 .(点)不起作用，而是 ,(逗号)起作用.

So it seems that the . (dot) is not working, but instead , (comma) is.

我已经检查了我的语言环境，但这应该不是问题.

I already checked my locale, but that shouldn't be the problem.

LANG="en_US.UTF-8"
LC_COLLATE="en_US.UTF-8"
LC_CTYPE="en_US.UTF-8"
LC_MESSAGES="en_US.UTF-8"
LC_MONETARY="en_US.UTF-8"
LC_NUMERIC="en_US.UTF-8"
LC_TIME="en_US.UTF-8"
LC_ALL="en_US.UTF-8"

推荐答案

您的 Scanner 可能正在使用 Denmark Locale 因为它使用 , 格式化双变量而不是美国默认的 ..

Your Scanner is probably using the Denmark Locale as it uses , to format double variables instead of US default ..

您可以通过以下方式检查它(我尝试在本地强制我的扫描仪使用丹麦语言环境，它的行为方式与您的实验中相同):

Here is how you can check it (I tried locally forcing my Scanner to use Denmark Locale and it behaves the same way as in your experiments):

Scanner sc = new Scanner(System.in);
System.out.println(sc.locale().getDisplayCountry());

如果是这种情况，您需要将其设置为使用美国 Locale 或任何其他您想要的:

If this is your case, you need to set it to use the US Locale or any other you want:

Scanner sc = new Scanner(System.in);
sc.useLocale(Locale.US);
System.out.println(sc.locale().getDisplayCountry());

或者，如果您需要同时接受 、 和 .，您可以简单地使用格式化程序.下面是一个使用 France 作为 Locale 的 NumberFormat 示例，它正确地格式化了 、 和 .:

Alternatively, if you need to accept both , and . you could simply use a formatter. Here is one example with NumberFormat using France as Locale, which formats correctly both , and .:

NumberFormat numberFormat = NumberFormat.getInstance(Locale.FRANCE);
double doubleComma = numberFormat.parse("5,0").doubleValue();
double doubleDot = numberFormat.parse("5.0").doubleValue();

在您的代码中，您将执行以下操作:

In your code you would do something like:

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

        NumberFormat numberFormat = NumberFormat.getInstance(Locale.FRANCE);
        double n = numberFormat.parse(sc.next()).doubleValue();
        System.out.println(n);
    } catch (ParseException e) {
        e.printStackTrace();
    }
} 

这篇关于双接受逗号而不是点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！