Java alternative of PHP's preg_replace_callback

Java alternative of PHP's preg_replace_callback

A quick implementation to have it at hand.

/**
 * Substitute for PHP's preg_replace_callback().
 */
public static final String replaceWithCallback(
                                String str, String regexp, StringsReplaceCallback cb)
{
        Pattern pat = Pattern.compile(regexp);
        return replaceWithCallback(str, pat, cb);
}


/**
 * Substitute for PHP's preg_replace_callback().
 */
public static final String replaceWithCallback(
                                String str, Pattern pat, StringsReplaceCallback cb
){
        Matcher mat = pat.matcher(str);

        StringBuilder sb = new StringBuilder(str.length() * 11 / 10);

        int prevStart = 0;
        int prevEnd = 0;
        int offset = 0;

        while( mat.find() ){

                // Create the groups array.
                String[] groups = new String[mat.groupCount()+1];
                for (int i = 0; i < groups.length; i++) {
                        groups[i] = mat.group(i);
                }

                // Append string before match.
                sb.append( str.substring(prevEnd+offset, mat.start()+offset) );

                // Call the callback and append what it returns.
                String newStr = cb.replace( groups );
                sb.append( newStr );

                // Set the offset according to the lengths difference.
                //offset -= mat.group().length();
                prevStart = mat.start() + offset;
                prevEnd = mat.end() + offset;
        }
        sb.append( str.substring(prevEnd) );

        return sb.toString();
}