Javascript Regex vs Java Regex

Question

I have a a regex in Javascript that works great: /:([\w]+):/g

I am working on converting my javascript app to java, and I know to escape the \ using \ i.e. /:([\\w]+):/g, yet my tests are still returning no match for the string "hello :testsmilie: how are you?"

    Pattern smiliePattern = Pattern.compile("/:([\\w]+):/g");
    Matcher m = smiliePattern.matcher(message);
    if(m.find()) {
        System.println(m.group(0));
     }

In javascript it returns ":testsmilie:" just fine, so i'm not sure what the difference is. Any help would be much appreciated!

Java uses a different set of rules than JavaScript, much like PHP vs JavaScript, JS doesnt allow look behinds and other sorts , google the differences — clearshot66
– clearshot66, Commented Nov 1, 2018 at 15:06

Youcef LAIDANI · Accepted Answer · 2018-11-01 15:14:12Z

5

Your regex in java can just be :

Pattern.compile(":[^:]+:")

Which match : followed by one or more no two dots : followed by :

Or if you want to use \w you can use :

Pattern.compile(":\\w+:")

If you note you don't need parenthesis of group (), so to get the result you can just use :

System.out.println(m.group());

edited Nov 1, 2018 at 15:14

answered Nov 1, 2018 at 15:09

Youcef LAIDANI

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azro · Accepted Answer · 2018-11-01 15:06:47Z

2

You should learn how is made a Javascript regex, because the / are the delimiters of the real regex, and g is a modifier for global

In Java the equivalent is: :([\\w]+):, and no need of global flag as you just need to call multiple times .find() to get all the matches

You should take a look at regex101 which is a good website to test regex

answered Nov 1, 2018 at 15:06

azro

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