StringUtil.isolateFirst(String, String)

/*
 * Utility class providing additional methods useful for string manipulation
 *
 * @version 0.1
 * @author  Marty Chang (Slalom Consulting)
 */
public class StringUtil {

    /*
     * @param  haystack The string
     * @param  regExp   The regular expression
     * @return The first substring of the string that matches the regular
     *         expression; <code>null</code> otherwise
     */
    public static String isolateFirst(String haystack, String regExp) {
        String match = null;

        // Attempt to split the haystack using the regular expression.
        // If the split successfully produces two "ends", use the
        // info about the ends to extract the match in the middle

        List<String> haystackEnds = haystack.split(regExp, 2);

        if (haystackEnds.size() == 2) {
            String frontEnd = haystackEnds.get(0);
            String backEnd = haystackEnds.get(1);

            match = haystack.substring(frontEnd.length(),
                haystack.length() - backEnd.length());
        }

        // Return the match

        return match;
    }
}