Thank you all for the valuable feedbacks and suggestions! :)

After experimenting a bit with regular expressions, this seems to do
the trick:

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

public class OSTest
{
        public static void main (String[] args)
        {
                String sIssue = "Red Hat 88 (Update 3456)";
                String sRegex = "\\d+[.]\\d+|\\d+";
                System.out.println (parseIssueFileForVersionNumber( sIssue, sRegex
));
        }

        private static String parseIssueFileForVersionNumber ( String sIn,
                String sPattern)
            {
                Pattern patternLanguage = Pattern.compile( sPattern );
                Matcher matcher = patternLanguage.matcher( sIn );

                   matcher.find();
                int nStart = matcher.start();
                int nStop = matcher.end();
                sIn = sIn.substring(  nStart,  nStop);               
                return sIn;
            }
}