Convert a String into a Regular Expression

[Alex Loaiza]

Hi, anyone knows if there is a way to convert an input string into a Regular Expression??

As a example, if I input the string: "[e-mail]" the output string should be like: "[A-Za-z]+@[A-Za-z]+\\.com"

Thanks in advance!!

[Jeff Albertson]

I don't think that's a well-defined question. There are many
regular expressions that could possibly match a given string, right?

[Steve Morrow]

Hi, anyone knows if there is a way to convert an input string into a Regular Expression??

There's no generic way to do that. There are innumerable regexes that would match that string.

[Alex Loaiza]

Well, in fact, what I need is: given a certain String verify if it is an alfanumeric string and covert it into a Reggex pattern like this [0-9\w], or if it is a numeric (numbers only) string convert it to [0-9]...

...I don't need a too complex solution, Thanks!!

[Ernest Friedman-Hill]

Now, if you had a bunch of strings, you can imagine a tool that would create the simplest possible regexp that matched them all. I'm sure such a thing has been done by someone... and indeed, I Googled for "regexp generator" and "regular expression generator" (both in quotes) and both returned many promising hits.

[Jeff Albertson]

Originally posted by Alex Loaiza:
Well, in fact, what I need is: given a certain String verify if it is an alfanumeric string and covert it into a Reggex pattern like this [0-9\w], or if it is a numeric (numbers only) string convert it to [0-9]...

Then why didn't your example convert the "com" at the end?

[Alex Loaiza]

Originally posted by Jeff Albrechtsen:

Then why didn't your example convert the "com" at the end?

Well, maybe I forget that ".com" at the end, but I think that you already understad what I meant. A simple reggex generator that matches in a "generic" way any input string given...

thanks!

[Jeff Albertson]

Something simple-minded like this:

public static String createRegex(String s) {
    StringBuilder b = new StringBuilder();
    for(int i=0; i<s.length(); ++i) {
        char ch = s.charAt(i);
        if ("\\.^$|?*+[]{}()".indexOf(ch) != -1)
            b.append('\\').append(ch);
        else if (Character.isLetter(ch))
            b.append("[A-Za-z]");
        else if (Character.isDigit(ch))
            b.append("\\d");
        else
            b.append(ch);
    }
    return b.toString();
}

[ November 18, 2005: Message edited by: Jeff Albrechtsen ]

[Alex Loaiza]

That's correct, just that simple!!

Thanks a lot!!