stackoverflow exception while using String match in java

Question

For a little university project i'm doing, i need to extract code samples from html given as a string. To by more precise, i need to get from that html string, everything in between <code> and </code>.

I'm writing in Java, and using String.match to do that.

My code:

public static ArrayList<String> extractByHTMLtagDelimiters(String source, String startDelimiter, String endDelimiter){
ArrayList<String> results = new ArrayList<String>();
if (source.matches("([\t\n\r]|.)*" + startDelimiter + "([\t\n\r]|.)*" + endDelimiter)){
    //source has some code samples in it
    //get array entries of the form: {Some code}</startDelimiter>{something else}
    String[] splittedSource = source.split(startDelimiter);
        for (String sourceMatch : splittedSource){
        if (sourceMatch.matches("([\t\n\r]|.)*" + endDelimiter + "([\t\n\r]|.)*")){
            //current string has code sample in it (with some body leftovers)
            //the code sample located before the endDelimiter - extract it
            String codeSample = (sourceMatch.split(endDelimiter))[0];
            //add the code samples to results
            results.add(codeSample);
        }
        }
}
return results;

iv'e tried to extract that samples from some html of ~1300 chars and got pretty massive exception: (it goes on and on for few dozens of lines)

Exception in thread "main" java.lang.StackOverflowError
at java.util.regex.Pattern$Branch.match(Unknown Source)
at java.util.regex.Pattern$GroupHead.match(Unknown Source)
at java.util.regex.Pattern$Loop.match(Unknown Source)
at java.util.regex.Pattern$GroupTail.match(Unknown Source)
at java.util.regex.Pattern$BranchConn.match(Unknown Source)
at java.util.regex.Pattern$CharProperty.match(Unknown Source)
at java.util.regex.Pattern$Branch.match(Unknown Source)
at java.util.regex.Pattern$GroupHead.match(Unknown Source)
at java.util.regex.Pattern$Loop.match(Unknown Source)
at java.util.regex.Pattern$GroupTail.match(Unknown Source)
at java.util.regex.Pattern$BranchConn.match(Unknown Source)
at java.util.regex.Pattern$CharProperty.match(Unknown Source)
at java.util.regex.Pattern$Branch.match(Unknown Source)
at java.util.regex.Pattern$GroupHead.match(Unknown Source)
at java.util.regex.Pattern$Loop.match(Unknown Source)
at java.util.regex.Pattern$GroupTail.match(Unknown Source)
at java.util.regex.Pattern$BranchConn.match(Unknown Source)
at java.util.regex.Pattern$CharProperty.match(Unknown Source)
at java.util.regex.Pattern$Branch.match(Unknown Source)
at java.util.regex.Pattern$GroupHead.match(Unknown Source)
at java.util.regex.Pattern$Loop.match(Unknown Source)

i've found the following bug report: https://bugs.java.com/bugdatabase/view_bug?bug_id=5050507

is there anything i can do to still use string.match? if not, can you please recommend some other way to do it without implementing html parsing by myself?

Thank a lot, Dub.

@khachik, if you bothered to look at the bug, you would realize it was closed as "Will not fix", as it's pretty fundamental to the way the regex library was written. So upgrading won't make any difference. — Matthew Flaschen
– Matthew Flaschen, Commented Apr 1, 2011 at 20:09
I'm useing the newest Java (i think, i updated few months ago), i just mentioned that iv'e encountered this problem in the web, and it look that in my java version it still exists. — Boris C
– Boris C, Commented Apr 1, 2011 at 20:11

wolfcastle · Accepted Answer · 2011-04-01 20:35:03Z

3

You can just manually go through the input string using String's indexOf() method to find the start and end deliminters and extract out the bits between yourself.

public static void main(String[] args) {
    String source = "<html>blah<code>this is awesome</code>more junk</html>";

    String startDelim = "<code>";
    String endDelim = "</code>";
    int start = source.indexOf(startDelim);
    int end = source.indexOf(endDelim);

    String code = source.substring(start + startDelim.length(), end);
    System.out.println(code);
}

If you need to find more than one, then just use indexOf again starting at the point you finished:

int nextStart = source.indexOf(startDelim, end + endDelim.length())

answered Apr 1, 2011 at 20:35

wolfcastle

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1 Comment

Boris C Over a year ago

Thanks, it did the job! somehow i always forget that the simplest solution might be the best.

Simon G. · Accepted Answer · 2011-04-01 20:45:51Z

1

Simply replace your regex pattern with "(?s).*"

This matches anything including new lines as you intended.

answered Apr 1, 2011 at 20:45

Simon G.

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1 Comment

Simon G. Over a year ago

Personally, I prefer the non-regex solution from wolfcastle.

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