Multiple backslashes in string java regex

Question

So I have a string X1X2X3\\\\. I only want to capture the AlphaNumerics values. My regex is ([A-z0-9]*).*. But it will return X1X2X3\\. My code looks like this:

Pattern pattern = Pattern.compile("([A-z0-9]*).*");
Matcher matcher = pattern.matcher(str);
matcher.matches();
return matcher.group(1);

Would like to find regex Answer. Not String.replaceAll() or replace() :)

Do you have a *string* ``X1X2X3\\\\``, or a *string literal* `"X1X2X3\\\\"`? Also, your regex is wrong as it `[A-z]` can match non-alphanumeric characters. — Wiktor Stribiżew, Dec 07 '16 at 08:14
String literal `assertThat(trimSpecialCharacters("X1X2X3\\\\"), is("X1X2X3"));` — Mihkel L., Dec 07 '16 at 08:16
I think the problem is in `A-z`, you want `A-Za-z` instead. `A-z` matches chars between `Z` and `a` which aren't letters. — radoh, Dec 07 '16 at 08:17

score 1 · Answer 1 · answered Dec 07 '16 at 08:23

The problem is with A-z in [A-z0-9], which can match non-alpha characters as well, namely the code points between Z and a.

The correct expression to use is [A-Za-z0-9] for alphanumeric characters, or the predefined character class \\w.

(credit goes to all those who pointed out the mistake in comments)

Multiple backslashes in string java regex

1 Answers1