String ResultString = null;
try {
    Pattern regex = Pattern.compile("(open|close|commit|total|insert)(?: (\\d+))?", Pattern.DOTALL);
    Matcher regexMatcher = regex.matcher(subjectString);
    if (regexMatcher.find()) {
        ResultString = regexMatcher.group();
    }
} catch (PatternSyntaxException ex) {
    // Syntax error in the regular expression
}