Question

I’m quite new to Java and I’m facing a situation I can’t solve. I have some html code and I’m trying to run a regular expression to store all matches into an array. Here’s my code:

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

    public class RegexMatch{
      boolean foundMatch = false;
      public String[] arrayResults;

      public String[] TestRegularExpression(String sourceCode, String pattern){
      try{
      Pattern regex = Pattern.compile(pattern, Pattern.CASE_INSENSITIVE | Pattern.MULTILINE);
      Matcher regexMatcher = regex.matcher(sourceCode);
      while (regexMatcher.find()) {
        arrayResults[matches] = regexMatcher.group();
        matches ++;
      } 
    } catch (PatternSyntaxException ex) {
      // Exception occurred
    }
    return arrayResults;
  }
}

I’m passing a string containing html code and the regular expression pattern to extract all meta tags and store them into the array. Here’s how I instantiate the method:

RegexMatch regex = new RegexMatch();
regex.TestRegularExpression(sourceCode, "<meta.*?>");
String[] META_TAGS = regex.arrayResults;

Any hint?
Thanks!

Answer 1

Firstly, parsing HTML with regular expressions is a bad idea. There are alternatives which will convert the HTML into a DOM etc – you should look into those.

Assuming you still want the “match multiple results” idea though, it seems to me that a List<E> of some form would be more useful, so you don’t need to know the size up-front. You can also build that in the method itself, rather than having state. For example:

import java.util.*;
import java.util.regex.*;

public class Test
{
    public static void main(String[] args)
        throws PatternSyntaxException
    {
        // Want to get x10 and x5 from this
        String text = "x10 y5 x5 xyz";
        String pattern = "x\\d+";
        List<String> matches = getAllMatches(text, pattern);
        for (String match : matches) {
            System.out.println(match);
        }
    }

    public static List<String> getAllMatches(String text, String pattern)
        throws PatternSyntaxException
    {
        Pattern regex = Pattern.compile(pattern);
        List<String> results = new ArrayList<String>();
        Matcher regexMatcher = regex.matcher(text);
        while (regexMatcher.find()) {
            results.add(regexMatcher.group());
        }
        return results;
    }
}

It’s possible that there’s something similar to this within the Matcher class itself, but I can’t immediately see it…