Regex in java to match a string begining with html followed by something

Question

Can someone help me out with a regex to match a string which starts with the following eg: The string can begin with any html tag eg: < span > or < p > etc so basically I want a regex to check if a string begins with any opening html tag <> and then followed by [apple videoID=

Eg:

<span>[apple videoID=

Here's what I've tried :

static String pattern =  "^<[^>]+>[apple videoID=";
static Pattern pattern1 = Pattern.compile(pattern);

What is wrong in the above?

[Obligatory link](http://stackoverflow.com/a/1732454/2846923) — The Guy with The Hat, Apr 11 '14 at 16:30
You have to implement a grammar of some sort to detect matching characters in a string. Regular expressions are called regular for a reason, it means they can only parse languages that can be described by finite state machines (automata) and matching characters would require infinite states. — Mdev, Apr 11 '14 at 16:34
what do you mean? It's a pattern that I'm compiling. Pattern.compile() — user3524469, Apr 11 '14 at 16:35
Oh, nevermind. If you know the amount of brackets you want then it's possible. — Mdev, Apr 11 '14 at 16:36
`[A-za-z]` This range seems to be wrong. It should be `[A-Za-z]` — Cruncher, Apr 11 '14 at 16:46
you need to escape `[` in `[apple videoID=`, as such : `\[apple videoID=` — njzk2, Apr 11 '14 at 19:48

score 2 · Answer 1 · answered Apr 11 '14 at 18:10

You have a typo in the following line.

static String pattern = "^<[^>]+>[apple videoID=";

This string is not a valid regular expression because you have an unclosed [ right before the word apple, hence the "Unclosed character class" PatternSyntaxException. You either meant to type

static String pattern = "^<[^>]+><apple videoID=";

assuming that apple is an html tag, or

static String pattern = "^<[^>]+>\\[apple videoID=";

if you really did want the [ in front of apple. This is because [ is a special character in regular expressions and must be escaped with a \ which is a special character in Java strings and must be escaped with a \. Therefore \\[.

Alexandru Severin · Answer 2 · 2014-04-11T19:17:42.427

0

simple as this:

<[.]+><apple videoID=[.]*

edited Apr 11 '14 at 19:17

answered Apr 11 '14 at 16:42

Alexandru Severin

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I think it should be <.*> – user3524469 Apr 11 '14 at 17:04
@Sam I've updated the post. Please check. That's not working for me. It says unclosed characeter class – user3524469 Apr 11 '14 at 17:29

score 0 · Answer 3 · edited Apr 12 '14 at 11:58

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Here is the solution

Pattern.CASE_INSENSITIVE helps to fetch the pattern either in upper case or lower case.

Tested and Executed.

    package sireesh.yarlagadda;

    import java.util.regex.Matcher;
    import java.util.regex.Pattern;

    public class Pattern {

        public static void main(String[] args) {
            String text="<span><apple videoID=";

            String patternString = "<[a-zA-Z]*>\\<apple videoID=";

            Pattern pattern = Pattern.compile(patternString, Pattern.CASE_INSENSITIVE);
            Matcher matcher = pattern.matcher(text);

            System.out.println("lookingAt = " + matcher.lookingAt());
            System.out.println("matches   = " + matcher.matches());
        }

    }

edited Apr 12 '14 at 11:58

aliteralmind

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answered Apr 11 '14 at 16:51

Sireesh Yarlagadda

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Oh I guess you got me wrong. I don't want to consider any html between the apple tag. I want to match the string which begins with 1 html tag. It could be span or p etc .. . 1 html tag followed by " – user3524469 Apr 11 '14 at 17:02
All the second asterisk does (`>*`) is match 0+ `>`s. [As you can see](http://regex101.com/r/rH9kH7), that will cause unintended consequences. – Sam Apr 11 '14 at 17:02
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Changed the solution to fit the requirement. Removed asterisk. Case sensitive is added. @Sam – Sireesh Yarlagadda Apr 11 '14 at 17:19
what's the point of `[a-zA-Z]` if you are using `CASE_INSENSITIVE` ? – njzk2 Apr 11 '14 at 19:49
You are right. It even works with [a-z] . Just to play safe. @njzk2 – Sireesh Yarlagadda Apr 11 '14 at 19:52

score 0 · Answer 4 · answered Apr 11 '14 at 19:46

0

Try this pattern :

"^<[A-Za-z]+>\\[apple videoID=$"

This pattern will match [apple videoID=

Hope this will help you..!

answered Apr 11 '14 at 19:46

Naresh Ravlani

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not a chance. the `^` and `$` means this must be a complete line. – njzk2 Apr 11 '14 at 19:55

Regex in java to match a string begining with html followed by something

4 Answers4