Regex pattern works in javascript but fails in scala with PatternSyntaxException: Unclosed character class

Question

Here is the regex:

ws(s)?://([0-9\.a-zA-Z\-_]+):([\d]+)([/([0-9\.a-zA-Z\-_]+)?

Here is a test pattern:

wss://beta5.max.com:18989/abcde.html

softlion.com likes it:

Test results
Match count: 1

Global matches:
wss://beta5.max.com:18989/abcde.html

Value of each capturing group:
0    1   2   3   4
wss://beta5.max.com:18989/abcde.html     s   beta5.max.com   18989   /abcde.html

scala does not:

val regex = """ws(s)?://([0-9\.a-zA-Z\-_]+):([\d]+)([/([0-9\.a-zA-Z\-_]+)?""".r


Exception in thread "main" java.util.regex.PatternSyntaxException: Unclosed character class near index 58
ws(s)?://([0-9\.a-zA-Z\-_]+):([\d]+)([/([0-9\.a-zA-Z\-_]+)?

WestCoastProjects · Accepted Answer · 2014-05-30 20:01:34Z

1

My bad, I had an extra [ at the front of the last capturing group.

([/([0-9.a-zA-Z-_]+)?

answered May 30, 2014 at 20:01

WestCoastProjects

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Comments

user557597 · Accepted Answer · 2014-05-30 22:03:12Z

1

Java allows intersections and all that, so error ..

     ws
     ( s )?
     ://
     ( [0-9\.a-zA-Z\-_]+ )
     :
     ( [\d]+ )
=    (  <-- Unbalanced  '('
=         [  <-- Unbalanced  '['
          /
          ( [0-9\.a-zA-Z\-_]+ )?

With everybody else its no problem:

 ws
 ( s )?                             # (1)
 ://
 ( [0-9\.a-zA-Z\-_]+ )              # (2)
 :
 ( [\d]+ )                          # (3)
 ( [/([0-9\.a-zA-Z\-_]+ )?          # (4)

So, its good to see (know) the original regex is not what you thought it was.

answered May 30, 2014 at 22:03

user557597

3 Comments

WestCoastProjects Over a year ago

I had not heard about intersections. How does the unbalanced ([ relate?

WestCoastProjects Over a year ago

Hi, did you get a chance to describe how the exta ([ relates to intersections? thx

user557597 Over a year ago

@javadba - Was gone, didn't see this. I've written so many regular expression parsers, it's all a blur. Java (and Python?) won't support inner (inside a class) raw opening bracket without a corresponding closing brace. Intersections are prefaced by && literals, unions aren't (which is irrelevant). With everybody else, you can include the opening bracket and its just a literal. Look at this docs.oracle.com/javase/tutorial/essential/regex/… for the gory details of java classes.

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