filtering collector

Main.java

package com.company;

import java.util.HashSet;
import java.util.Set;
import java.util.function.BiConsumer;
import java.util.function.BinaryOperator;
import java.util.function.Function;
import java.util.function.Supplier;
import java.util.stream.Collector;

public class Main {

    static class Person {
        final int id;
        final String name;

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

        @Override
        public String toString() {
            return "Person{" +
                    "id=" + id +
                    ", name='" + name + '\'' +
                    '}';
        }
    }

    static void save(Person person) {
        if (person.name == null) {
            throw new NullPointerException("name is null");
        }
    }

    public static void main(String[] args) {
        Set<Person> input = new HashSet<>();
        input.add(new Person(1, "1"));
        input.add(new Person(2, null));
        input.add(new Person(3, "3"));

        Set<Person> outout = input.stream().collect(new Collector<Person, Set<Person>, Set<Person>>() {

            @Override
            public Supplier<Set<Person>> supplier() {
                return HashSet::new;
            }

            @Override
            public BiConsumer<Set<Person>, Person> accumulator() {
                return (people, person) -> {
                    try {
                        save(person);
                        people.add(person);
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                };
            }

            @Override
            public BinaryOperator<Set<Person>> combiner() {
                return (people, people2) -> {
                    people.addAll(people2);
                    return people;
                };
            }

            @Override
            public Function<Set<Person>, Set<Person>> finisher() {
                return people -> people;
            }

            @Override
            public Set<Characteristics> characteristics() {
                HashSet<Characteristics> characteristics = new HashSet<>();
                characteristics.add(Characteristics.IDENTITY_FINISH);
                return characteristics;
            }
        });

        System.out.println(String.format("inout: %s", input));
        System.out.println(String.format("output: %s", input));
        input.removeAll(outout);
        System.out.println(String.format("invalid: %s", input));
    }
}

inout: [Person{id=2, name='null'}, Person{id=1, name='1'}, Person{id=3, name='3'}]
output: [Person{id=2, name='null'}, Person{id=1, name='1'}, Person{id=3, name='3'}]
invalid: [Person{id=2, name='null'}]