Update nested list of objects using java stream api

Question

I have this class:

public class StructUserType extends UserType {

    MembersList membersList = new MembersList();

    public List<Member> getMembers() {
        return Collections.unmodifiableList(membersList.members);
    }

    static class MembersList {
        List<Member> members = new ArrayList<>();
    }

    public static class Member implements Identifiable {
        private Integer id;
        private String name;
        //getters and setters
    }    
}

And I have a List of object:

List<UserType> userTypes = new ArrayList<>();

I want update Member object which is equal to a certain id. For example, update the name field of member by id. How I can update nested list using stream api?

UPDATE:

I did this:

In class StructUserType I created one method:

void updateMember(Member member) {
        membersList.members.stream()
                .filter(m -> m.getId().equals(member.getId()))
                .findFirst()
                .ifPresent(m -> {
                    m.setName(member.getName());
                    m.setUserTypeId(member.getUserTypeId());
                });
    }

Also for external clients created a public method:

public void updateMemberOfStructUserType(StructUserType.Member member) {
        userTypes.stream()
                .filter(StructUserType.class::isInstance)
                .map(StructUserType.class::cast)
                .filter(st -> st.getMembers()
                        .stream()
                        .anyMatch(m -> m.getId().equals(member.getId())))
                .findFirst()
                .ifPresent(structUserType -> structUserType.updateMember(member));
    }

What is userTypes and the type SmbpUserType? What does that have to do with StructUserType? Do you have any code attempts at a streams solution, or any thoughts about how you might code it? — rgettman
– rgettman, Commented Feb 23, 2018 at 18:54
Can you update your question to provide a general overview of level of nesting that you are talking about? In the question I can see a list List<Member> and that's about it. — Raf
– Raf, Commented Feb 23, 2018 at 19:26
@Raf, I have List<UserType>, UserType contains List<Member>. I want update member by Id of this member, for example, set new name field. I updated my question, how can I made this. But I think, my method not optimal. — All_Safe
– All_Safe, Commented Feb 23, 2018 at 19:30
Much better. What is the result you are getting when you run this? Does it not update? Or you are getting an exception or some other result? — Raf
– Raf, Commented Feb 23, 2018 at 19:39
@Raf, It's work perfect, it update. But, I think this is not the optimal solution, because In fact, the same filter works twice in the first method, and then in the second. — All_Safe
– All_Safe, Commented Feb 23, 2018 at 19:44

Calculator · Accepted Answer · 2018-02-23 20:19:14Z

You can flatmap the userTypes in the public update method and pass a stream of members to a common private updateMember method:

private void updateMember(Member member, Stream<Member> membersStream){
    membersStream.filter(m -> m.getId().equals(member.getId()))
        .findFirst()                
        .ifPresent(m -> {
            m.setName(member.getName());
            m.setUserTypeId(member.getUserTypeId());
        });
}

void updateMember(Member member) {
    updateMember(member, membersList.members.stream());        
}

public void updateMemberOfStructUserType(StructUserType.Member member) {
    Stream<Member>  membersStream = userTypes.stream()
        .filter(StructUserType.class::isInstance)
        .map(StructUserType.class::cast)
        .flatMap(st -> st.getMembers().stream());    
    updateMember(member, membersStream);
}

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