CODEWITHSUNDEEP
javaregex
Thang Pham
Thang Pham

Reputation: 38695

validate decimal with decimal separator and thousand separator

Hi I used this regex for validate number with decimal separator and thousand separator 

ets = "\\,";
eds = "\\.";
"^([+\\-]?[0-9" + ets + "]*(" + eds + "[0-9]*)?)$"

But this fail (it accept when it should not) for two of my unit test case,

12., and 1,,2, anyone can help please?

Note: This work for 1..2.

Upvotes: 3

Views: 2721

Answers (2)

NullUserException
NullUserException

Reputation: 85478

Let's look at the actual regex that is used:

^([+\-]?[0-9\,]*(\.[0-9]*)?)$

This matches 12. because your second part is (\.[0-9]*). Note that * means zero or more, so digits are optional.

This also matches 1,,2 because you included the comma in the first character class [0-9\,]. So actually your regex would match ,,,,,,,, as well.

This can be solved without regexes, but if you need a regex, you'd probably want something like this:

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

Broken down:

^ # match start of string
 [+-]? # matches optional + or - sign
 [0-9]{1,3} # match one or more digits 
 (,[0-9]{3})* # match zero or more groups of comma plus three digits
 (\. # match literal dot
  [0-9]+ # match one or more digits
 )? # makes the decimal portion optional
$ # match end of string

To use this in Java you'd want something like:

ets = ","; // commas don't need to be escaped
eds = "\\."; // matches literal dot

regex = "^[+-]?[0-9]{1,3}(" + ets + "[0-9]{3})*(" + eds + "[0-9]+)?$"

Upvotes: 7

Cristobal De Leon
Cristobal De Leon

Reputation: 89

If I understand correctly, 12. matches because you are matching 0 or 1 occurences of (a period, then 0 or more ocurrences of any number between 0 and 9). So you may have a period and nothing in front of it.

1,,2 matches because you are matching 0 or more occurences of any characters between 0 and 9, or a comma. therefor you could have 0,,,,,,,,,,,,,,0.

If you want the last one not to match, make sure you can only have up to 3 numbers before a comma (in the thousand separator) using curly braces to indicate the amount of ocurrences allowed (i. e. {0,3}) after a set of numbers.

[0-9]{0,3},

@NullUserException just gave a complete regexp that works for your intentions

Upvotes: 1

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