Currently dubbo support java6, java7 and java8.

All unit test pass in java9, we should consider add official support for java9 and even java10.
Currently travis support java9. java10 is in progress (https://github.com/travis-ci/travis-ci/issues/9368)

As discussed in mail list, the first step is to add java9 in travis ci.
Class<?> clazz = NAME_CLASS_CACHE.get(name);
        if (clazz == null) {
            clazz = Class.forName(name, true, cl);
            NAME_CLASS_CACHE.put(name, clazz);
        }
        return clazz;
    }
    /**
     * desc to class.
     * "[Z" => boolean[].class
     * "[[Ljava/util/Map;" => java.util.Map[][].class
     *
     * @param desc desc.
     * @return Class instance.
     * @throws ClassNotFoundException
     */
    public static Class<?> desc2class(String desc) throws ClassNotFoundException {
        return desc2class(ClassHelper.getClassLoader(), desc);
    }
    /**
     * desc to class.
     * "[Z" => boolean[].class
     * "[[Ljava/util/Map;" => java.util.Map[][].class
     *
     * @param cl   ClassLoader instance.
     * @param desc desc.
     * @return Class instance.
     * @throws ClassNotFoundException
     */
    private static Class<?> desc2class(ClassLoader cl, String desc) throws ClassNotFoundException {