Review

• missing/call
• superfluous/call

class DateUtil {
    /**
     * Formats the given date according to the specified pattern.  The pattern
     * must conform to that used by the {@link SimpleDateFormat simple date
     * format} class.
     * 
     * @param date The date to format.
     * @param pattern The pattern to use for formatting the date.  
     * @return A formatted date string.
     * 
     * @throws IllegalArgumentException If the given date pattern is invalid.
     * 
     * @see SimpleDateFormat
     */
    public static String formatDate(Date date, String pattern) {
        if (date == null) throw new IllegalArgumentException("date is null");
        if (pattern == null) throw new IllegalArgumentException("pattern is null");
        
        SimpleDateFormat formatter = new SimpleDateFormat(pattern);
        formatter.setTimeZone(GMT);
        return formatter.format(date);
    }

}