Method of

base/src/main/java/net/time4j/engine/TimeSpan.java:335–342

(
            long amount,
            U unit
        )

         * @throws  IllegalArgumentException if amount is negative
         */
        public static <U> Item<U> of(
            long amount,
            U unit
        ) {

            return new Item<>(amount, unit);

        }

        /**
         * <p>Yields the non-negative amount. </p>