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Regular expression in Java for parsing money

I’m looking for are regex for parsing money amounts. The String s10 should not match. Can someone help, or can someone simplify the regex? That’s my try:

    public static String[] getMoney(String s) {
        List<String> ret = new ArrayList<String>();
        String regex = "((\d{1,3}[.,]?)(\d{3}[.,]?)*[.,]\d{1,2})(\D|$)";
        Pattern pat = Pattern.compile(regex);
        Matcher mat = pat.matcher(s);
        while (mat.find()) {
            ret.add(mat.group(1));
        }
        return ret.toArray(new String[0]);
    }

    public static void main(String[] args) {
        String s1 = "0,1"; // should match
        String s2 = ",1"; // should not match
        String s3 = "1,"; // should not match
        String s4 = "1.234,01"; // should match
        String s5 = "1234,10"; // should match
        String s6 = "1234,100"; // should not match
        String s7 = "1234,10a"; // should match
        String s8 = "123,456,789.10"; // should match
        String s9 = "123.456.789,10"; // should match
        String s10 = "123,456.789,10"; // should not match (!)

        System.out.println(Arrays.toString(getMoney(s1)));
        System.out.println(Arrays.toString(getMoney(s2)));
        System.out.println(Arrays.toString(getMoney(s3)));
        System.out.println(Arrays.toString(getMoney(s4)));
        System.out.println(Arrays.toString(getMoney(s5)));
        System.out.println(Arrays.toString(getMoney(s6)));
        System.out.println(Arrays.toString(getMoney(s7)));
        System.out.println(Arrays.toString(getMoney(s8)));
        System.out.println(Arrays.toString(getMoney(s9)));
        System.out.println(Arrays.toString(getMoney(s10)));
    }

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Answer

I think you may use

(?<![d,.])(?:d{1,3}(?:(?=([.,]))(?:1d{3})*)?|d+)(?:(?!1)[.,]d{1,2})?(?![,.d])

See the regex demo

Details

  • (?<![d,.]) – no digit, . or , allowed immediately on the left
  • (?:d{1,3}(?:(?=([.,]))(?:1d{3})*)?|d+) –
    • d{1,3}(?:(?=([.,]))(?:1d{3})*)? – one, two or three digits followed with an optional occurrence of a position followed with a comma or dot followed with 0 or more occurrences of the captured value and then any three digits
    • |d+ – or 1 or more digits
  • (?:(?!1)[.,]d{1,2})? – an optional sequence of a comma or dot, but not the same char as in Group 1, and then 1 or 2 digits
  • (?![,.d]) – no digit, . or , allowed immediately on the right

In Java, do not forget to double the backslashes:

String regex = "(?<![\d,.])(?:\d{1,3}(?:(?=([.,]))(?:\1\d{3})*)?|\d+)(?:(?!\1)[.,]\d{1,2})?(?![,.\d])";
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