* @param clazz
     *            The wrapper class. Must not be {@literal null}.
     * @return The primitive class if the argument is a wrapper class, otherwise {@literal null}.
     */
    public static Class<?> getPrimitiveClass(final Class<?> clazz) {
        assertArgumentNotNull("clazz", clazz);

        return wrapperToPrimitiveMap.get(clazz);
    }

    /**