* <p>
     * Usage example:
     * </p>
     *
     * <pre>
     * StringUtil.decamelize("UserId")  = "USER_ID"
     * </pre>
     *
     * @param s
     *            the text
     * @return the resulting string
     */
    public static String decamelize(final String s) {
        if (s == null) {
            return null;
        }
        if (s.length() == 1) {