How to find the number of occurrences of characters from a regular expression in a string?

Question

Java

Regular expression - "\\W | _"(any character except alphabetic and numeric).
You need to count the number of such characters in a string.

Answer 1

You have an error in the regular expression, parentheses are needed here:

String st = "q!w_e*"
Pattern pattern = Pattern.compile("(\\W)|(_)");
Matcher matcher = pattern.matcher(st);
long matches = matcher.results().count();
System.out.println(matches);

The output, respectively, in this example is 3