Method set

base/src/main/java/net/time4j/Duration.java:4264–4280

(
            long amount,
            IsoUnit unit
        )

        }

        private void set(
            long amount,
            IsoUnit unit
        ) {

            for (int i = 0, n = this.items.size(); i < n; i++) {
                if (this.items.get(i).getUnit() == unit) {
                    throw new IllegalStateException("Already registered: " + unit);
                }
            }

            if (amount != 0) {
                Item<IsoUnit> item = Item.of(amount, unit);
                this.items.add(item);
            }

        }

        private void update(
            long amount,