Java Regex does not match newline

Question

My code is as follows:

public class Test {
    static String REGEX = ".*([ |\t|\r\n|\r|\n]).*";
    static String st = "abcd\r\nefgh";

    public static void main(String args[]){
        System.out.println(st.matches(REGEX));
    }
}

The code outputs false. In any other cases it matches as expected, but I can't figure out what the problem here is.

Answer 1

You need to remove the character class.

static String REGEX = ".*( |\t|\r\n|\r|\n).*";

You can't put \r\n inside a character class. If you do that, it would be treated as \r, \n as two separate items which in-turn matches either \r or \n. You already know that .* won't match any line breaks so, .* matches the first part and the next char class would match a single character ie, \r. Now the following character is \n which won't be matched by .*, so your regex got failed.