确定String是否为数字并使用Java进行转换？ [英] Determine if a String is a number and convert in Java?

问题描述

我知道之前经常会问过这个问题的变体（参见此处和此处例如），但不 完全重复。

I know variants of this question have been asked frequently before (see here and here for instance), but this is not an exact duplicate of those.

我想检查是否字符串是一个数字，如果是这样，我想将它存储为 double 。有几种方法可以做到这一点，但所有这些方法似乎都不适合我的目的。

I would like to check if a String is a number, and if so I would like to store it as a double. There are several ways to do this, but all of them seem inappropriate for my purposes.

一种解决方案是使用 Double.parseDouble（s ）或类似的新的BigDecimal 。但是，如果存在逗号，则这些解决方案不起作用（因此1,234会导致异常）。我当然可以在使用这些技术之前删除所有逗号，但这似乎会在其他语言环境中造成大量问题。

One solution would be to use Double.parseDouble(s) or similarly new BigDecimal(s). However, those solutions don't work if there are commas present (so "1,234" would cause an exception). I could of course strip out all commas before using these techniques, but that would seem to pose loads of problems in other locales.

我查看了Apache Commons NumberUtils.isNumber（s），但遭受相同的逗号问题。

I looked at Apache Commons NumberUtils.isNumber(s), but that suffers from the same comma issue.

我考虑过 NumberFormat 或 DecimalFormat ，但这些似乎太宽松了。例如，1A被格式化为1而不是表示它不是数字。此外，像127.0.0.1这样的东西将被算作数字127而不是表明它不是数字。

I considered NumberFormat or DecimalFormat, but those seemed far too lenient. For instance, "1A" is formatted to "1" instead of indicating that it's not a number. Furthermore, something like "127.0.0.1" will be counted as the number 127 instead of indicating that it's not a number.

我觉得我的要求不是那么异国情调我是第一个这样做的人，但没有一个解决方案完全符合我的需要。我想即使我不知道完全我需要什么（否则我可以编写自己的解析器），但我知道上述解决方案因指示的原因不起作用。是否存在任何解决方案，或者我是否需要准确弄清楚我需要什么并为其编写自己的代码？

I feel like my requirements aren't so exotic that I'm the first to do this, but none of the solutions does exactly what I need. I suppose even I don't know exactly what I need (otherwise I could write my own parser), but I know the above solutions do not work for the reasons indicated. Does any solution exist, or do I need to figure out precisely what I need and write my own code for it?

推荐答案

声音很奇怪，但我会尝试按照这个答案并使用 java.util.Scanner 。

Sounds quite weird, but I would try to follow this answer and use java.util.Scanner.

Scanner scanner = new Scanner(input);
if (scanner.hasNextInt())
    System.out.println(scanner.nextInt());
else if (scanner.hasNextDouble())
    System.out.println(scanner.nextDouble());
else
    System.out.println("Not a number");

对于 1A 等输入， 127.0.0.1 ， 1,234 ， 6.02e-23 我得到了以下输出：

For inputs such as 1A, 127.0.0.1, 1,234, 6.02e-23 I get the following output:

Not a number
Not a number
1234
6.02E-23

Scanner.useLocale 可用于更改到期望的地区。

Scanner.useLocale can be used to change to the desired locale.

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