CODEWITHSUNDEEP
javaregex
Alex DaSilva
Alex DaSilva

Reputation: 289

How would I use regex to allow certain characters?

Mainly I am using regex, and what my code does essentially, is sends a client return code if it does not contain the characters in regex. My problem is, I do not know how to allow spaces. Currently this is my code, I would like to have allow a space, a-z, A-Z and 0-9.

if (username.length() < 1 || username.length() >= 13
    || !username.matches("[a-zA-Z_0-9]"))
{
    session.getLoginPackets().sendClientPacket(3);
    return;
}

Upvotes: 1

Views: 1038

Answers (4)

Scott Weaver
Scott Weaver

Reputation: 7361

use the \w metasequence (words, letters, underscores), plus a space (or \s to match tabs too), in a character class:

var pattern = @"[\w ]{1,12}"; //c#, validates length also.

edit: this seems to work for single spacing only, does not validate the length though:

var pattern = @"^(\w+\s?)+$";

Upvotes: 2

stema
stema

Reputation: 93086

I am quite sure you want to be Unicode compliant, so you should use

[\p{L}\p{Nd}][\p{L}\p{Nd} ]*

I created two character classes to ensure that it is not starting with a space, if this check is not needed, just remove the first class and change the quantifier of the second to a +.

From regular-expressions.info

\p{Nd} or \p{Decimal_Digit_Number}: a digit zero through nine in any script except ideographic scripts.

\p{L} or \p{Letter}: any kind of letter from any language.

More about Unicode in Java

Upvotes: 2

mattnz
mattnz

Reputation: 33

Try this one 

if (username.length() < 1 || username.length() >= 13
    || !username.matches("[a-zA-Z0-9 ]+"))
    {
        session.getLoginPackets().sendClientPacket(3);
        return;
    }

Upvotes: 1

Babak Naffas
Babak Naffas

Reputation: 12581

The regex you're looking for is [a-zA-Z_0-9][a-zA-Z_0-9 ]* assuming you don't want a name to start with spaces.

Upvotes: 2

Related Questions