Regex Java Illegal/unsupported escape sequence

Question

I'm searching for a "color=number,number,number" and get the "number,number,number" part using regex but when I put the regex pattern,

I get: Regular expression '"\bcolor=\b\K\w\d,\d*,\d*"' is malformed: Illegal/unsupported escape sequence*

Here is the code:

    Pattern p = Pattern.compile("\\bcolor=\\b\\K\\w\\d*,\\d*,\\d*");
    Matcher m = p.matcher(url);
    if(m.find()){
        return m.group(0);
    }
    else {
        return "0,0,0";
    }

I also tried:

    "\\bcolor=\\b\\\\K\\w\\d*,\\d*,\\d*"

and:

    "\\\\bcolor=\\\\b\\\\K\\\\w\\\\d*,\\\\d*,\\\\d*"

The above compiles but doesn't get the desired result.

How can I fix this? Thanks!

Does Java even support \K?

Biffen
– Biffen

2018-04-20 09:30:00 +00:00
Commented Apr 20, 2018 at 9:30 — Biffen
– Biffen, Commented Apr 20, 2018 at 9:30

Wiktor Stribiżew · Accepted Answer · 2018-04-20 09:30:51Z

2

The \K match reset operator is not supported by the regex engine in Android. You can safely use a capturing group around the part of the regex you want to extract and then grab it using .group(1):

Pattern p = Pattern.compile("\\bcolor=(\\w\\d*,\\d*,\\d*)");
Matcher m = p.matcher(url);
if(m.find()){
    return m.group(1);
}
else {
    return "0,0,0";
}

Note you do not need the second \b word boundary as it is implicit between a = (non-word char) and \w (matches a word char).

Details

\bcolor= - color= as a whole word
(\w\d*,\d*,\d*) - Capturing group #1: a word char, 0+ digits, and 2 occurrences , followed with , and 0+ digits. You may even write it as (\\w\\d*(?:,\\d*){2}).

answered Apr 20, 2018 at 9:30

Wiktor Stribiżew

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