泛型ArrayList转数组

 @SuppressWarnings("unchecked")    public static <T> T[] toArray(Class<?> cls, ArrayList<T> items) {        if (items == null || items.size() == 0) {            return (T[]) Array.newInstance(cls, 0);        }        return items.toArray((T[]) Array.newInstance(cls, items.size()));    }