Generate a random value from a regex

[nimo frey]

Hello,

How can I generate a randomly word which lays in the domain of the regex "[a-zA-Z]+" ?

For example:

// pseudo code
String randomWord = Randomize.viaRegex([a-zA-Z]+);

randomWord can be "aa" or aZd" and so on.

[Henry Wong]

Regular expressions are used to find/match and extract stuff. It doesn't have anything that generates (random or otherwise) in the API.

Henry

[David Newton]

In other words, you'd have to write it. Fortunately it's really easy, at least for the regex you provide.

[nimo frey]

okay I will try it to code.


I googled a lot and found that:

http://stackoverflow.com/questions/205411/random-string-that-matches-a-regexp

can I use perl within java? If so, then I can use something like this (this solution is from the link above):

print random_regex('[A-Za-z]{3}[0-9][A-Z]{2}[!@#$%^&*]'), "\n";

or do I have to use somethink like this solution (the solution is from the link http://stackoverflow.com/questions/54991/generating-random-passwords):

public string CreatePassword(int length)
        {
            string valid = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890";
            string res = "";
            Random rnd = new Random();
            while (0 < length--)
                res += valid[rnd.Next(valid.Length)];
            return res;
        }

[David Newton]

Nimo wrote:can I use perl within java?

Er, no.

[fred rosenberger]

will you need to dynamically generated the output based on user supplied regex input? or will it ALWAYS be a-zA-Z?

Basically, you need to determine what the range of values is. a-z is 26 values, and then A-Z is another 26. That means you need to generate a number from 1-52. you then need to map your numbers to your output values.

[nimo frey]

hello,

or will it ALWAYS be a-zA-Z?

yes, this is what I want.

In perl, does Java has a similar method like perls "random_regex" ? Should I use perl within java? Is that possible?

[Jesper de Jong]

So, you have the fixed regular expression "[a-zA-Z]+" and you want to generate a random word that matches it? That's easy: generate a random number (>= 1) of lower-case and upper-case letters and concatenate them. No need to bother with difficult things such as trying to use Perl from Java (which is not easy). Java has no built-in method like Perl's random_regex.

Or do you want to be able to do this for arbitrary regular expressions?

[fred rosenberger]

since you're always doing a-zA-Z, i'd just write a method that converts the numbers 1-52 to your letters. Then, generate random numbers between 1-52 inclusive.

it shouldn't be hard at all.

[nimo frey]

okay will try it and post the code..

[Velu Kasirajah]

Did you take look at org.apache.commons.lang.RandomStringUtils class? This class has a variety of methods that may suit your needs.

For instance, the following code will return a randomized string of 10 chars.

 RandomStringUtils.randomAlphabetic(10) 

[nimo frey]

hello Velu,

thank you!

that really fulfills my needs!! thanks!

[Velu Kasirajah]

Glad it helped