import java.util.ArrayList;
import java.util.List;

import static java.util.stream.Collectors.toList;

public class DemoStream {
    // 新插入的集合元素（newlist）中，如果老的集合元素（oldlist）中有，就不插入進去，過濾出oldlist沒有的元素
    public static void main(String[] args) {
        List<User> oldList = new ArrayList<>();
        User user1 
 
= new User("1", "張三1");
        User user2 = new User("2", "張三2");
        User user3 = new User("3", "張三3");
        User user4 = new User("4", "張三3");
        oldList.add(user1);
        oldList.add(user2);
        oldList.add(user3);
        oldList.add(user4);

        List<User> newList = new
 
 ArrayList<>();
        User user5 = new User("1", "張三1");
        User user6 = new User("6", "張三6");
        User user7 = new User("7", "張三7");
        User user8 = new User("8", "張三8");
        newList.add(user5);
        newList.add(user6);
        newList.add(user7);
        newList.add(user8);

        System.out.println(
 
"===========過濾出老集合中沒有的所有元素===========");
        List<User> resultList = newList.stream().filter(item ->
                !oldList.parallelStream().map(User::getId).collect(toList()).contains(item.getId())
        ).collect(toList());

        resultList.forEach(m1 -> {
            System.out.println(m1);
        });
    }
}

class User {
    private String id;
    private String name;

    public String getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

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

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

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

結果：