Java regex to check if string is valid number format (comma and decimal point placing)

Question

1000 - valid
1,000 - valid
1,000.00 - valid
1000.00 - valid
1000.00.00 - invalid
1,0.00 - invalid
1,000,00.00 - invalid
1,000,000.12 - valid

no of decimal places can be unlimited

I've been trying to find the right regex pattern, can't seem to find one that will accomodate all validations. Can anyone help

the pattern ^[1-9]\d{0,2}(.\d{3})*(,\d+)?$ did not work for me, based from the similar thread here

Possible duplicate of [Decimal or numeric values in regular expression validation](http://stackoverflow.com/questions/2811031/decimal-or-numeric-values-in-regular-expression-validation) — royB, Mar 15 '17 at 23:32
the pattern ^[1-9]\d{0,2}(.\d{3})*(,\d+)?$ did not work for me, based from that similar thread — Hingle McJingleberry, Mar 15 '17 at 23:38
@Alain Del Rosario try using ^[1-9]\d*(\,\d+)?$ . You can try the regex script with sample input on this site http://www.regexplanet.com/advanced/java/index.html — Arthur Decker, Mar 15 '17 at 23:41
i think validations from that link treats commas as required not optional — Hingle McJingleberry, Mar 15 '17 at 23:54
If there are thousand separators before the decimal point, do they need to be there after the point too? Are both 1,111,111.111,111,1 and 1,111,111.1111111 valid? — Ole V.V., Mar 16 '17 at 00:00
@AlainDelRosario, please remember to accept an answer if you find one of the four acceptable. Excuse me for mentioning, but it seems you were good at accepting answers in January, I hope you are not starting to forget? — Ole V.V., Mar 19 '17 at 19:01

score 3 · Answer 1 · answered Mar 16 '17 at 00:40

3

This is one of possible regexes you are looking for:

^\d{1,3}([ ,]?\d{3})*([.,]\d+)?$

Demo: https://regex101.com/r/T8tcDP/1

answered Mar 16 '17 at 00:40

streetturtle

5,472
2
25
43

This pattern shows "10,00" as valid and ".05" as invalid. – johnw182 Jan 20 '23 at 19:19
Also negatives dont work with this. – johnw182 Jan 20 '23 at 19:23

score 3 · Accepted Answer · answered Mar 16 '17 at 23:47

You should try this expression:

^\d{1,3}|\d(([ ,]?\d{3})*([.,]\d{2}+)?$)

With this expression is covered with the scenarios raised.

Here the complete example:

public class Decimal {

    private static String REGEX = "^\\d{1,3}|\\d(([ ,]?\\d{3})*([.,]\\d{2}+)?$)";

    public static void main(String[] args) {
        String data[] = {"1000", "1,000", "1,000.00", "1000.00", "1000.00.00", "1,0.00", "1,000,00.00", "1,000,000.12"};

        Pattern.compile(REGEX);

        for (int i = 0; i < data.length; i++) {
            if (data[i].matches(REGEX)) {
                System.out.println(data[i] + " - valid");
            } else {
                System.out.println(data[i] + " - invalid");
            }
        }
    }

}

The output:

1000 - valid
1,000 - valid
1,000.00 - valid
1000.00 - valid
1000.00.00 - invalid
1,0.00 - invalid
1,000,00.00 - invalid
1,000,000.12 - valid

score 0 · Answer 3 · answered Mar 16 '17 at 00:14

This would match your numbers there (?:\d+(?:,\d{3})*(?:\.\d{2})?|\.\d{2})
It would also match .00 just incase. If you don't want it to, just remove
the |\.\d{2} part.

Add your own boundary constructs as needed ^$ or \b

Expanded

 (?:
      \d+ 
      (?: , \d{3} )*
      (?: \. \d{2} )?
   |  \. \d{2} 
 )

score 0 · Answer 4 · answered Mar 16 '17 at 00:15

My suggestion is:

^[1-9]((\d{0,2}(,\d{3})*(\.(\d{3},)*\d{1,3})?)|(\d*(\.\d+)?))$

A number either has separators for every 3 digits or it hasn’t (no middle forms). It either has a decimal point and at least one digit after it, or it hasn’t. In all cases does it start with a non-zero digit.

Remember that a dot (period, .) has a special meaning in regex and therefore needs to be escaped to get a literal point.

Java regex to check if string is valid number format (comma and decimal point placing)

4 Answers4

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