Java 8によるListにおけるオブジェクト属性のデリバリー

public class Person {
        private int id;

        private String name;

        public Person(int id, String name) {
            this.id = id;
            this.name = name;
        }

        public int getId() {
            return id;
        }

        public void setId(int id) {
            this.id = id;
        }

        public String getName() {
            return name;
        }

        public void setName(String name) {
            this.name = name;
        }

}

public class Test {
        public static void main(String[] args) {
            Person p1 = new Person(1, "11");
            Person p2 = new Person(1, "22");
            Person p3 = new Person(2, "11");
            List persons = Arrays.asList(p1,p2,p3);
            List unique = persons.stream().collect(
                    Collectors.collectingAndThen(
                            Collectors.toCollection(() -> new TreeSet<>(Comparator.comparing(Person::getId))), ArrayList::new)
            );
            unique.forEach(p -> System.out.println(p.getId()));
        }
}