Method build

base/src/main/java/net/time4j/Duration.java:4251–4262

()

         * @return  new {@code Duration}
         */
        public Duration<IsoUnit> build() {

            if (this.items.isEmpty()) {
                throw new IllegalStateException("Not set any amount and unit.");
            }

            return new Duration<>(
                this.items,
                this.negative
            );

        }

        private void set(
            long amount,