Java Collections.EMPTY_LIST与Collections.emptyList()的区别

    /**
     * The empty list (immutable).  This list is serializable.
     *
     * @see #emptyList()
     */
    @SuppressWarnings("unchecked")
    public static final List EMPTY_LIST = new EmptyList<>();

 /**
     * Returns the empty list (immutable).  This list is serializable.
     *
     * <p>This example illustrates the type-safe way to obtain an empty list:
     * <pre>
     *     List<String> s = Collections.emptyList();
     * </pre>
     * Implementation note:  Implementations of this method need not
     * create a separate <tt>List</tt> object for each call.   Using this
     * method is likely to have comparable cost to using the like-named
     * field.  (Unlike this method, the field does not provide type safety.)
     *
     * @see #EMPTY_LIST
     * @since 1.5
     */
    @SuppressWarnings("unchecked")
    public static final <T> List<T> emptyList() {
        return (List<T>) EMPTY_LIST;
}

protected Map<String, String> optionalStrParams = Collections.emptyMap();

protected Map<String, String> optionalStrParams = new HashMap<String, String>();