Regular Expression program from Predefined character classes

Question

public class RegularExpressionDemo2 {

    public static void main(String[] args) {
        Pattern p = Pattern.compile("\\.");
        Matcher m = p.matcher("a1b7 @z#");
        while (m.find()) {
            System.out.println(m.start() + "-------" + m.group());
        }
    }
}

From the docs, it says the . symbol prints any character then How come the above program doesn't print any thing.

Because you're escaping the `.` (with a backslash), making it match literal `.`s. — Biffen, Apr 29 '15 at 09:29

score 1 · Accepted Answer · answered Apr 29 '15 at 09:29

1

You double-escaped the dot.

This means you are matching a literal dot, not a wildcard for any character.

Your input does not contain one, hence nothing gets printed.

Change the Pattern to ".".

answered Apr 29 '15 at 09:29

Mena

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If i don't double escape then it gives error "illegal escape character" at that line – kittu Apr 29 '15 at 09:30
2

@kittu `"."`, not `"\."`. – Biffen Apr 29 '15 at 09:31
@kittu what JDK / IDE are you using? That should definitely **not** happen. – Mena Apr 29 '15 at 09:31
Thanks it works. Actually I shouldn't escape it at all unlike other patterns – kittu Apr 29 '15 at 09:31

Regular Expression program from Predefined character classes

1 Answers1