How to create a regex for accepting only alphanumeric characters?

Question

Possible Duplicate:
Regular Expression for alphanumeric and underscores

Thanks.

http://stackoverflow.com/questions/336210/regular-expression-for-alphanumeric-and-underscores — Damian Leszczyński - Vash, May 13 '11 at 06:50
`^[a-zA-Z0-9_+-]*$` the '-' must be the last thing in case you need it too — Aquarius Power, May 24 '17 at 03:59

score 110 · Answer 1 · edited Mar 17 '14 at 12:27

110

Try below Alphanumeric regex

"^[a-zA-Z0-9]*$"

^ - Start of string

[a-zA-Z0-9]* - multiple characters to include

$ - End of string

See more: http://docs.oracle.com/javase/7/docs/api/java/util/regex/Pattern.html

edited Mar 17 '14 at 12:27

pintxo

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answered May 13 '11 at 06:49

niksvp

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This will also match an EMPTY string, which may not be desirable in most situations. To counter that simply replace the trailing `*` with `+` So basically it's `^[a-zA-Z0-9]+$` to avoid false positives generated by empty strings. You can also text your regex at https://regex101.com/ – Ivan Jun 03 '20 at 09:12

score 28 · Answer 2 · answered May 13 '11 at 07:00

28

[a-zA-Z0-9] will only match ASCII characters, it won't match

String target = new String("A" + "\u00ea" + "\u00f1" +
                             "\u00fc" + "C");

If you also want to match unicode characters:

String pat = "^[\\p{L}0-9]*$";

answered May 13 '11 at 07:00

Frank Schmitt

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Given +1 for Unicode, as this is often overlooked. – Steve Eynon Jan 07 '16 at 13:31

score 18 · Answer 3 · answered May 13 '11 at 06:55

18

Only ASCII or are other characters allowed too?

^\w*$

restricts (in Java) to ASCII letters/digits und underscore,

^[\pL\pN\p{Pc}]*$

also allows international characters/digits and "connecting punctuation".

answered May 13 '11 at 06:55

Tim Pietzcker

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Note: it's important to say that \w accepts underscore. – lcjury Aug 17 '16 at 19:29
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Yes, that's what I wrote in my answer. – Tim Pietzcker Aug 17 '16 at 20:56

score 4 · Answer 4 · answered May 13 '11 at 06:55

4

try with \w

http://download.oracle.com/javase/tutorial/essential/regex/pre_char_classes.html

answered May 13 '11 at 06:55

Torres

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this is old but just so people know, this also matches underscores – Philippe Paré Aug 30 '18 at 13:21

score 3 · Answer 5 · edited May 23 '17 at 12:10

3

Use this ^[a-zA-Z0-9_]*$

See here for more info.

edited May 23 '17 at 12:10

Community

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answered May 13 '11 at 06:51

ace

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score 2 · Answer 6 · answered May 13 '11 at 06:50

2

see http://download.oracle.com/javase/1.5.0/docs/api/java/util/regex/Pattern.html

for example [A-Za-z0-9]

answered May 13 '11 at 06:50

pintxo

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this will accept only numbers as well – Optimist Rohit Jan 28 '22 at 07:41

How to create a regex for accepting only alphanumeric characters?

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