Regex Unclosed character class in Java; escaping doesn't solve issue [duplicate]

Question

I have this regex in JS flavor

^[\w.-]+(?:\.[\w\.-]+)+[\w\-\._~:/?#[\]@!\$&'\(\)\*\+,;=.]+$

I tried it in JS and it worked for me (only want to match URL that does not start with the HTTP/HTTPS protocol): https://regex101.com/r/6y2Gnd/2

Now I want to use the same regex in my Java backend. At first I got the error

Unclosed character class

Upon reading into it, I realized I have to escape the \ slash. I basically added three \\\ to every \ slash. The result is:

^[\\\\w.-]+(?:\\\\.[\\\\w\\\\.-]+)+[\\\\w\\\\-\\\\._~:/?#[\\\\]@!\\\\$&'\\\\(\\\\)\\\\*\\\\+,;=.]+$

Even though the compiler doesn't show any errors anymore, the result was empty, i.e. it couldn't match the cases like it did with in JS flavor.

I tested the Java regex here and in my code.

www.web.de # I want to match this
web.de # I want to match this
http://web.de # I do NOT want to match this
https://www.web.de # I do NOT want to match this

Anyone know what I'm missing?

Why are you turning a single '\' into '\\\\'? Have you tried just '\\'? — Jason
– Jason, Commented Feb 23, 2020 at 23:40
@Jason Yes, I've tried that too: ^[\\w.-]+(?:\\.[\\w\\.-]+)+[\\w\\-\\._~:/?#\[\\]@!\\$&'\$\$\\*\\+,;=.]+$. Still no matches. I escaped because of Java. I've been told that java behaves like that. — thadeuszlay
– thadeuszlay, Commented Feb 23, 2020 at 23:43
Like so? ^[\\w.-]+(?:\\.[\\w\\.-]+)+[\\w\\-\\._~:/?#\[\\]@!\\$&'\$\$\\*\\+,;=.]+$? — thadeuszlay
– thadeuszlay, Commented Feb 23, 2020 at 23:51

Marko Medojević · Accepted Answer · 2020-02-23 23:44:02Z

0

Following regex works well in Java regex tester:

^[\w.-]+(?:\.[\w\.-]+)+[\w\-\._~:/?#\[\]@!\$&'\(\)\*\+,;=.]+$

Please try it yourself. Backslash should be added in the front of the [ character.

answered Feb 23, 2020 at 23:44

Marko Medojević

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3 Comments

thadeuszlay Over a year ago

I added ^[\w.-]+(?:\.[\w\.-]+)+[\w\-\._~:/?#\[\]@!\$&'\*\+,;=.]+$ into freeformatter.com/java-regex-tester.html#ad-output But no matches found

Marko Medojević Over a year ago

I just tested and it works. Multiline checkbox should be selected.

thadeuszlay Over a year ago

Yes, you are right! It's working

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