regex causing logic error

Question

private final String reg2 = "[A-Z][A-Za-z0-9_]+@[a-z]+[.com|.net][.sg|.cn|.au]?";

this line of code is supposed to be the regex for an email tester. the current email I'm using to test it is [email protected](imaginary of course). However, it seems to be always wrong. How do I change it?

"[A-Z][A-Za-z0-9_]+@[a-z]+(?:\\.com|\\.net)(?:\\.sg|\\.cn|\\.au)?" — Avinash Raj
– Avinash Raj, Commented Mar 26, 2015 at 16:05
You seem to lack a basic understanding of regex ([.com|.net]). May I suggest you start with a tutorial? — Biffen
– Biffen, Commented Mar 26, 2015 at 16:06
"However, it seems to be always wrong" Your problem is obvious here, but in general, you can get better answers if you describe what you expect and what it does instead. — Andy Turner
– Andy Turner, Commented Mar 26, 2015 at 16:06

Wiktor Stribiżew · Accepted Answer · 2015-03-26 16:09:43Z

3

It will be wrong because you are using character classes instead of alternative groups.

(\.com|\.net) - this is correct.

Your regex can match "[email protected]" after a small enhancement (see demo here):

[A-Z][A-Za-z0-9_]+@[a-z]+(?:\.com|\.net)(?:\.sg|\.cn|\.au)?

See more on alternative lists here and on character classes here.

edited Mar 26, 2015 at 16:09

answered Mar 26, 2015 at 16:05

Wiktor Stribiżew

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3 Comments

Avinash Raj Over a year ago

see he uses two charcater class not one. Don't combine the both.

Wiktor Stribiżew Over a year ago

It is just a sample to check "[email protected]". But you are right. :)

Andy Turner Over a year ago

I believe that he was intending to match e.g. .com.au, since that is a common domain in Australia, not .com or .au.

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