Question

I want to replace any one of these chars:

% \ , [ ] # & @ ! ^

… with empty string (“”).

I used this code:

String line = "[ybi-173]";
Pattern cleanPattern = Pattern.compile("%|\\|,|[|]|#|&|@|!|^");
Matcher matcher = cleanPattern.matcher(line);
line = matcher.replaceAll("");

But it doesn’t work.

What do I miss in this regular expression?

Answer 1

There are several reasons why your solution doesn’t work.

Several of the characters you wish to match have special meanings in regular expressions, including ^, [, and ]. These must be escaped with a \ character, but, to make matters worse, the \ itself must be escaped so that the Java compiler will pass the \ through to the regular expression constructor. So, to sum up step one, if you wish to match a ] character, the Java string must look like "\\]".

But, furthermore, this is a case for character classes [], rather than the alternation operator |. If you want to match “any of the characters a, b, c, that looks like [abc]. You character class would be [%\,[]#&@!^], but, because of the Java string escaping rules and the special meaning of certain characters, your regex will be [%\\\\,\\[\\]#&@!\\^].