Java Pattern Match For ALphanumeric

[chitra lekha]

Hi

I need to validate whether the given string is alphanumeric or not and take the decision based on it.
I am using java pattern for the same with regex.

Pattern p = Pattern.compile("^[A-Za-z0-9]+$");
p.matcher(s).matches()

It shud return false if the string passed contains only number or only letters or any special charaters.

And true if the string contains both numeric and letters present in any order.

However with above pattern its returning true when I am entering "234" or "abcd".

Please let me know what should be the regular expression used here.

[Balagopal Kannampallil]

This link has a similar problem and solution discussed.

[Ulf Dittmer]

ASCII only? Or can there be accented characters?

[fred rosenberger]

Personally, I would probably not try to write a single regex to do it all...I'd make several tests in separate methods.

If your requirements change in a week or a month, it's much easier to add or delete them that way than by coming up with one convoluted expression. Something like

doesContainAlpha()
doesContainNum()
onlyContainAlphanum()

all these would return a boolean, then my if-condition would work of those results.

[Richard Tookey]

My approach would be to use

        Pattern p = Pattern.compile("(?:"
                + "[a-zA-Z]+[0-9]+"  // Only letter(s) followed by digit(s)
                + "|"                // or
                + "[0-9]+[a-zA-Z]+"  // only digit(s) followed by letter(s)
                + ")"
                + "[a-zA-Z0-9]*");   // with the rest of the line being either letters or digits

or

            Pattern p = Pattern.compile("(?=.*[0-9])" // There is a digit
                    + "(?=.*[a-zA-Z])"                 // there is a letter
                    + "[a-zA-Z0-9]*");                 // there are only letters and digits

[chitra lekha]

Hi Richard,

Thanks a lot got the solution to my problem. This is the solution which I have used.

Pattern p = Pattern.compile("(?=.*[0-9])" // There is a digit
+ "(?=.*[a-zA-Z])" // there is a letter
+ "[a-zA-Z0-9]*");

[fred rosenberger]

Richard Tookey wrote:My approach would be to use...

Same concept...the different tests are still separated out, so they can easily be changed/added to/amended when the requirements change.