java - 使用 java Stream api 更新对象的嵌套列表

Question

我有这门课:

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
    }    
} 

我有一个对象的列表:

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

我想要更新等于某个 id 的 Member 对象。例如，通过id更新member的name字段。如何使用 stream api 更新嵌套列表？

更新:

我这样做了:

在类StructUserType中我创建了一个方法:

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());
                });
    }

还为外部客户端创建了一个公共(public)方法:

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));
    }

Answer 1

您可以在公共(public)更新方法中平面映射userTypes，并将成员流传递给公共(public)私有(private)updateMember 方法:

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);
}