java - Java中检查字符串是否有小数部分 : Locale involved

Question

我有一个String值，它可以保存Long或Double。 String 可能是基于Locale 的。

因此它可能包含以下值:

11
11.00
15,25 (for Locale like Denmark where the decimal part is denoted by a comma instead of dot)

只有当它是 Double 时我才想做某事；从某种意义上说，它包含一个分数值。小数值“00”也是有效的情况。

if(string contains fraction){
  // do something
}

根据上面的三个示例，对于 11.00 和 15,25，控制应该放在 if 内部，但对于 11，则不应该。

我怎样才能检查这个？

请记住，涉及区域设置。因此点和逗号对于不同的区域设置可能有不同的含义。因此，简单的正则表达式来查找它们的出现是行不通的。例如如果区域设置为澳大利亚，则 11,00 为 1100，因此不是 double 。但如果区域设置是丹麦或德国等欧洲国家，则 11,00 是双倍。

我需要使用 NumberFormat 找到一些解决方案，但无法解决。

我有区域设置信息。所以我知道字符串是否属于哪个区域设置。鉴于此，我怎样才能知道字符串是否有分数？

Answer 1

编辑:由于您已经编辑了您的问题，表明您知道区域设置，因此您可以将其与 NumberFormat.getNumberInstance(locale).parse(strValue) 结合使用逗号的正则表达式和千位分隔符。这是测试代码:

import java.text.DecimalFormatSymbols;
import java.text.NumberFormat;
import java.text.ParseException;
import java.util.Locale;

class Main{
  private static final Locale DUTCH = new Locale("nl","NL");

  public static void main(String[] a){
    test("11", Locale.ENGLISH);
    test("11", DUTCH);
    System.out.println();
    test("11.00", Locale.ENGLISH);
    test("11.00", DUTCH);
    System.out.println();
    test("11,00", Locale.ENGLISH);
    test("11,00", DUTCH);
    System.out.println();
    test("15.123", Locale.ENGLISH);
    test("15.123", DUTCH);
    System.out.println();
    test("15,123", Locale.ENGLISH);
    test("15,123", DUTCH);
    System.out.println();
    test("something", Locale.ENGLISH);
    test("something", DUTCH);
  }

  static void test(String val, Locale locale){
    try{
      DecimalFormatSymbols symbols = new DecimalFormatSymbols(locale);
      char decimalSep = symbols.getDecimalSeparator();
      char thousandSep = symbols.getGroupingSeparator();

      String escapedDecimalSep = decimalSep == '.' ? "\\." : decimalSep+"";
      String escapedThousandSep = thousandSep == '.' ? "\\." : thousandSep+"";

      String intRegex = "\\d+(" + escapedThousandSep + "\\d{3})*"; // Example ENGLISH: "\\d+(,\\d{3})*"
      String doubleRegex = intRegex + escapedDecimalSep + "\\d+"; // Example ENGLISH: "\\d+(,\\d{3})*\\.\\d+"

      NumberFormat format = NumberFormat.getInstance(locale);
      Number number = format.parse(val);
      if(val.matches(doubleRegex)){
        double d = number.doubleValue();
        System.out.println(val + " (in locale " + locale + ") is a double: " + d);
      } else if(val.matches(intRegex)){
        int i = number.intValue();
        System.out.println(val + " (in locale " + locale + ") is an integer: " + i);
      } else{
        System.out.println("Unable to determine whether value " + val + " is an integer or double for locale " + locale);
      }
    } catch(ParseException ex){
      System.out.println("Error occurred for value \"" + val + "\". Are you sure it's an integer or decimal?");
    }
  }
}

Try it online.

这是输出:

11 (in locale en) is an integer: 11
11 (in locale nl_NL) is an integer: 11

11.00 (in locale en) is a double: 11.0
Unable to determine whether value 11.00 is an integer or double for locale nl_NL

Unable to determine whether value 11,00 is an integer or double for locale en
11,00 (in locale nl_NL) is a double: 11.0

15.123 (in locale en) is a double: 15.123
15.123 (in locale nl_NL) is an integer: 15123

15,123 (in locale en) is an integer: 15123
15,123 (in locale nl_NL) is a double: 15.123

Error occurred for value "something". Are you sure it's an integer or decimal?
Error occurred for value "something". Are you sure it's an integer or decimal?