Regex gives error

Question

Continuing with the post at http://stackoverflow.com/questions/705672/regular-expression-to-allow-a-set-of-characters-and-disallow-others/705990#705990

Does anybody know why the below would occur?

I get the below error when I create a regular expression as:

[^@*–’”“\r\nœçsÇSgGšcrŠRNEŽDTCnežuUIti—¿„”]+

and enter any of these restricted characters in the input field

java.lang.ArrayIndexOutOfBoundsException
    at org.apache.regexp.RECompiler$RERange.delete(RECompiler.java:1326)
    at org.apache.regexp.RECompiler$RERange.remove(RECompiler.java:1417)
    at org.apache.regexp.RECompiler$RERange.include(RECompiler.java:1459)
    at org.apache.regexp.RECompiler$RERange.include(RECompiler.java:1470)
    at org.apache.regexp.RECompiler.characterClass(RECompiler.java:699)
    at org.apache.regexp.RECompiler.terminal(RECompiler.java:863)
    at org.apache.regexp.RECompiler.closure(RECompiler.java:942)
    at org.apache.regexp.RECompiler.branch(RECompiler.java:1151)
    at org.apache.regexp.RECompiler.expr(RECompiler.java:1203)
    at org.apache.regexp.RECompiler.compile(RECompiler.java:1281)
    at org.apache.regexp.RE.(RE.java:495)
    at org.apache.regexp.RE.(RE.java:480)

but this expression works perfectly fine

[^@*–’”“\r\nœçsÇSgGšcrŠRN]+

Also,

[^@*–’”“\r\nœçsÇSgGšcrŠR„”]+

works but

[^@*–’”“\r\nœçsÇSgGšcrŠRNE]+

does not work and gives the above error.

Is there a limit to the number of characters that can be disallowed like the way above?

Regards, Udit Sud

Answer 1

Looks like some error in apache regexp parser. Can you use a standart one (java.util.regex)?

Answer 2

I'm not a big Regex man myself, but here are 3 regex testing sites that might help:

http://www.txt2re.com/index.php3
http://gskinner.com/RegExr/
http://regex.larsolavtorvik.com/

Answer 3

The dash (minus sign) has special meaning in character classes. It defines ranges of consecutive characters, like "a-z".

There may exist a consecutive range for "*–’", but I guess this is not your intention. You probably wanted the literal dash, and I suspect the exception you are seeing has something to do with this.

Instead of this:

[^@*–’”“\r\nœçsÇSgGšcrŠRNEŽDTCnežuUIti—¿„”]+
----^ (this is the error)

Try:

[^@*’”“\r\nœçsÇSgGšcrŠRNEŽDTCnežuUIti—¿„”–]+
-----------------------------------------^ (this okay)

or

[-^@*’”“\r\nœçsÇSgGšcrŠRNEŽDTCnežuUIti—¿„”]+
-^ (this okay as well)

or

[^@*\–’”“\r\nœçsÇSgGšcrŠRNEŽDTCnežuUIti—¿„”]+
----^^ (this okay as well)

Answer 4

Thanks all, using the standard parser works fine. Thanks for all your help. -Udit.

Answer 5

See http://webui.sourcelabs.com/jakarta-regexp/issues/22804 -- an old version of this package did limit the maximum number of allowed ranges, to 16. This was fixed in 2003, but it's conceivable that they just raised the limit a little bit. (?)

Anyway, I always use the Java built-in Regex parser for any new work, as others have suggested.