public static <T> List<T> emptyIsDefault(final List<T> list, final List<T> defaultV) {
        return CollectionUtils.isEmpty(list) ? defaultV : list;
    }
if list is empty, return default value.

@param list     list
@param defaultV default value
@param <T>      list type
@return default value or list
shenyu-common/src/main/java/org/apache/shenyu/common/utils/ListUtil.java