Java 8 Optional multi-level null check

Question

I am working on a program that consumes methods which return Optional and I need to iterate over that and create a new object. How do I do that?

import java.util.Optional;

class Info {
    String name;
    String profileId;

    Info(String name, String profileId) {
        this.name = name;
        this.profileId = profileId;
    }
}

class Profile {
    String profileId;
    String profileName;

    Profile(String profileId, String profileName) {
        this.profileId = profileId;
        this.profileName = profileName;
    }
}

class Content {
    String infoName;
    String profileName;

    Content(String infoName, String profileName) {
        this.infoName = infoName;
        this.profileName = profileName;
    }

    public java.lang.String toString() {
        return "Content{" + "infoName='" + infoName + '\'' + ", profileName='" + profileName + '\'' + '}';
    }
}

class InfoService {
    Optional<Info> findByName(String name){ //todo implementation }
}

class ProfileService {
   Optional<Profile> findById(String id) { //todo implementation }
}

class ContentService {

    Content createContent(Info i, Profile p) {
        return new Content(i.name, p.profileName);
    }

    Content createContent(Info i) {
        return new Content(i.name, null);
    }
}

public static void main(String[] args) {

    InfoService infoService = new InfoService();
    ProfileService profileService = new ProfileService();
    ContentService contentService = new ContentService();

    //setup
    Info i = new Info("info1", "p1");
    Profile p = new Profile("p1", "profile1");

    // TODO: the following part needs to be corrected
    Optional<Info> info = infoService.findByName("info1");

    if (!info.isPresent()) {
        return Optional.empty();
    } else {
         Optional<Profile> profile = profileService.findById(info.get().profileId);

         Content content;

         if (!profile.isPresent()) {
             content = contentService.createContent(info);
         } else {
             content = contentService.createContent(info, profile);
         }

        System.out.println(content);
     }
}

My understanding of the Java Optional is to reduce the if null checks but I still can't do it without the if checks. Is there a better solution to use map or flatMap and have a concise code?

The simplicity of the question doesn't match the complexity of your example. Please rephrase (if it's indeed a complex problem) or simplify the example to an MCVE — Mark Jeronimus
– Mark Jeronimus, Commented Nov 14, 2018 at 13:08
@nullpointer can you explain what you mean? This code is a re-write of what I am doing (I don't want to use the same Models used in the company codebase) — biniam
– biniam, Commented Nov 14, 2018 at 13:08
if (!info.isPresent()) { return Optional.empty(); } I meant this part specifically within a void method, — Naman
– Naman, Commented Nov 14, 2018 at 13:11

biniam · Accepted Answer · 2018-11-14 14:53:52Z

8

This is the about the best you can get. map will only execute the lambda if it's present. orElseGet will only execute the lambda if it's not.

return infoService.findByName("info1")
    .map(info ->
        profileService.findById(info.profileId)
            .map(profile -> contentService.createContent(info, profile))
            .orElseGet(() -> contentService.createContent(info))
    );

edited Nov 14, 2018 at 14:53

biniam

8,2479 gold badges51 silver badges58 bronze badges

answered Nov 14, 2018 at 13:09

Michael

44.5k12 gold badges98 silver badges143 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

biniam Over a year ago

Nice one, Michael. Is there a way to chain infoService.findByName() at the beginning using map or flatMap to make the code even more concise?

Michael Over a year ago

@bak Yeah, just needs another map call. Edited my answer

Collectives™ on Stack Overflow

Java 8 Optional multi-level null check

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related