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.
public static final char JVM_DOUBLE = 'D';
    /**
     * float(F).
     */
    public static final char JVM_FLOAT = 'F';
    /**
     * int(I).
     */
    public static final char JVM_INT = 'I';
    /**
     * long(J).
     */
    public static final char JVM_LONG = 'J';
    /**
     * short(S).
     */
    public static final char JVM_SHORT = 'S';
    public static final Class<?>[] EMPTY_CLASS_ARRAY = new Class<?>[0];
    public static final String JAVA_IDENT_REGEX = "(?:[_$a-zA-Z][_$a-zA-Z0-9]*)";
    public static final String JAVA_NAME_REGEX = "(?:" + JAVA_IDENT_REGEX + "(?:\\." + JAVA_IDENT_REGEX + ")*)";
    public static final String CLASS_DESC = "(?:L" + JAVA_IDENT_REGEX + "(?:\\/" + JAVA_IDENT_REGEX + ")*;)";
    public static final String ARRAY_DESC = "(?:\\[+(?:(?:[VZBCDFIJS])|" + CLASS_DESC + "))";
    public static final String DESC_REGEX = "(?:(?:[VZBCDFIJS])|" + CLASS_DESC + "|" + ARRAY_DESC + ")";
    public static final Pattern DESC_PATTERN = Pattern.compile(DESC_REGEX);
    public static final String METHOD_DESC_REGEX = "(?:(" + JAVA_IDENT_REGEX + ")?\\((" + DESC_REGEX + "*)\\)(" + DESC_REGEX + ")?)";
    public static final Pattern METHOD_DESC_PATTERN = Pattern.compile(METHOD_DESC_REGEX);
    public static final Pattern GETTER_METHOD_DESC_PATTERN = Pattern.compile("get([A-Z][_a-zA-Z0-9]*)\\(\\)(" + DESC_REGEX + ")");
    public static final Pattern SETTER_METHOD_DESC_PATTERN = Pattern.compile("set([A-Z][_a-zA-Z0-9]*)\\((" + DESC_REGEX + ")\\)V");
    public static final Pattern IS_HAS_CAN_METHOD_DESC_PATTERN = Pattern.compile("(?:is|has|can)([A-Z][_a-zA-Z0-9]*)\\(\\)Z");
    private static final ConcurrentMap<String, Class<?>> DESC_CLASS_CACHE = new ConcurrentHashMap<String, Class<?>>();