apex regex validation. for version number string

Question

I am trying to validate a version number string. something like #.#.#.#

can you please tell me if the below is correct

^[0-9]{1,2}(.[0-9]{1,2})?

how do i restrict this to just 4 decimals?

Answer 1

The regex you provided does not give information regarding number of decimal places. You have to specify that. You have specify pattern to have 4 decimals and each number can be at max 2 digits.

// First, instantiate a new Pattern object "MyPattern"
Pattern MyPattern = Pattern.compile('[0-9]{1,2}.[0-9]{1,2}.[0-9]{1,2}.[0-9]{1,2}');

// Then instantiate a new Matcher object "MyMatcher"
Matcher MyMatcher = MyPattern.matcher('10.1.2.22');

// You can use the system static method assert to verify the match
System.assert(MyMatcher.matches());

Answer 2

There are plenty of Regex testers/fiddles out there, e.g. http://refiddle.com/

^\d\.\d\.\d\.\d$ expresses "Start string, digit, literal period, digit, period, digit, period, digit, end string"

Edit: Better yet, ^(\d\.){3}\d$ "start, 3 of (digit followed by period), and a digit.

Edit the second: assuming you're looking at IP addresses or anything else with a fixed number of digits between dots, up to 3 digits are permitted between periods: ^(\d{1,3}\.){3}\d{1,3}$