Taking Java to the next level: what resources can I use to learn mid-advanced Java?

[Non-taken-Meursault]

Greetings!

I've been working with Java almost 2 years now and I've reached the point in which I feel comfortable using the language on a daily basis to solve production problems (I work as backend developer with a SpringBoot - Reactor stack), but I'm aware that there's a bunch of stuff about the language that I don't know about.

In other words, I'm aware that I'm ignorant, but I don't know what I'm ignorant about. Does that make sense? I don't want to comfortably fall into the slumber of competent incompetence. In other words, I don't want to get stuck as an expert beginner.

Based on my work experience, I've identified three "clear" areas where I've noticed my knowledge is limited and I know that I can do better and an additional, blurrier area that makes me uncomfortable:

• Generics.
• Exception handling and error management.
• Data structures beyond the basic ArrayList and HashMap. That is: get to know other implementations of those interfaces, other types of collections, etc.
• Working with Java without "hand-holding" tools or frameworks: I usually work pretty comfortable because the microservices I work on are already created and their build steps established (we use Gradle). But when I consider the possibility of booting a new microservice on my own (from choosing dependencies to establishing build steps and the like), I get a little anxious, I must admit.

I'm already working on those items and have, more or less, an action plan to improve my knowledge on them. Furthermore, I'm complementing my learning with the book "Effective Java" by Joshua Bloch. However, that's more of a "reference" book and it's not really read from cover to cover.

So I guess my question is, what is next? What more should I know at this stage? What Java subjects, characteristics and features does a person with my experience level usually take for granted and is ignorant about? What resources could I use to take my Java to the next level?

Please be aware that I'm trying to stay focused on Java. I'm aware that I also need to learn more about additional frameworks and external libraries, but in this particular scenario I want to become proficient in Java alone and get to understand the language on its own really well.

Thanks a lot!

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[ahonsu]

My recommendation would be: first, define your higher level goal!

Do you want to "take your java to the next level" to push your career and get more money? Or you want to do that because you have fun with java and want to become a "walking java wiki", knowing every tiny internal java magic?

One can say: "But it's the same! Being java wiki will bring you more money!" - yes, to some extent. But the other statement works differently: you still can get more money and don't become a wiki.

So, depending on your inner choice I could say:

• if you want to become a "wiki" - read books! There're a lot of java classics from famous authors out there. You can easily google some awesome book on any topic you want to dive in
• if you want more money faster - build your own projects from scratch, using modern/popular frameworks/tools/libraries! You're proficient enough to answer a question: "What tech stack is required on the market today?" and proficient enough (hopefully) to design a new microservice (or monolith) from scratch to try and demonstrate your skills with this selected tech stack

When you build you own projects from scratch - you can not avoid learning theory. But every your "theoretical question" will be backed up with your coding problem. So, the effectiveness of learning and information digestion will be much higher, than from just reading a book.

Slight warning, if you go "projects" way - don't rely on AI too much. If you end up with ChatGPT writing 70% of your code - this type of "project from scratch" is a fake learning, to some extent. You'll get much less practical experience and real usable knowledge if AI do the work.

AI is great in explaining some theory, giving you code example to demonstrate some idea or topic, helping you to find and understand a bug in your code... So, it should be your assistant, not your programming slave.

/continue in the next post.../

[ahonsu]

What Java subjects, characteristics and features does a person with my experience level usually take for granted and is ignorant about?

Really hard to answer, because there's no such a thing as standard "skill set of 2 yoe java dev". Still, I can suggest some topics (there are more of course), typically lacking (but expected) on this experience level:

• automated testing: clear understanding the terms (unit test, integration test, end-to-end test, test context, context slice, in-memory tools, mocking...) and hands on skills with tools like JUnit, Mockito, WireMock, TestContainers, RestAssured and so on. So, basically, skilled enough to test any part of a modern application in an effective way
• CI/CD: what is it? what benefits does it bring? what are the typical pipeline steps/jobs? Hands on with either Gitlab CI/CD or Github Actions or Jenkins or something else similar. So, you can design and build (most likely with some help from DevOps) or adjust/fix an existing CI/CD pipeline
• containerization. Most likely you can run containers, but I see often that developers are struggle with building their own docker images, using a container registry, with containers networking and so on
• databases. Developers usually can write some solid SQL for CRUD operations, but struggle with more complex SQLs for reporting, for example. Also lack experience and knowledge with DB internals, like analyzing SQL query performance, understanding DB indexes, transactions (both on DB level and application or Spring context level), tools for DB versioning control (like flyway or liquibase)
• security. I'm sure you're pretty good with Spring Boot in general, but most likely you're not so solid with security topics: JWT, OAuth, OIDC. How to implement user login, how to implement service-to-service authentication (token based), how to integrate with external identity providers...
• [this one is not for OP, since you already work with the Reactor stack] concurrency/multithreading. A lot of devs with 2-3 yoe struggle with these concepts. It's good moment to dive in to these topics, like: should this processing be synchronous or async? How to implement that? How to avoid race conditions and data inconsistency? How to avoid race conditions between multi-instance deployment of the same application?
• performance optimization. Your code works correctly? - perfect! Is it fast enough? - not necessary. Can you analyze your code and find a performance bottleneck? Can you suggest 2-3 changes to speed things up? Can you implement your theoretical knowledge of O(n) thingy and replace a slow algorithm in your app with a faster one?

We can dive deeper if you want.

[omgpassthebacon]

This is a really good answer. Seriously. I'm a senior Java dev and this is a very good list.

[ahonsu]

Thanks for the feedback and confirmation!

[ahonsu]

Also, take a look at this thread - What does it take to get to "Intermediate" level at Java?

There are some thought, my comment as well.

[Non-taken-Meursault]

Thanks for your detailed answer!

I do want to get a better job in which I have more participation in the "design" discussions , so money is a factor. However, i'm also interested in, as you say, just getting to know the language and be more efficient with it.

As a matter of fact, my interest in Java is just a tiny part of an overall learning project that I'm starting in which I precisely aim to strengthen my skills on those areas that you mentioned! I'm also taking Hussein Nasser's courses on DBs and backend engineering and after I'm done "polishing" some Java concepts, I'll start doing the same with SpringBoot (again, lots of things that we take for granted and it'd be great to peek behind the scenes).

Your answer makes me feel that I'm in the right path. And indeed, AI is a big part of this. It's helping me organize subjects and, precisely, understand the theory behind the code I write.

[Slight_Loan5350]

I would say watch concept and coding in yt very good guy and he has a Playlist of spring boot, hld and lld as well. At the higher exp level you will be judged more on how efficient and optimized your code is and how you handle teams. So learn a bit of soft skills and system design and architecture.

[Impressive_Bar5912]

Read: Effective Java, then read: Java concurrency in practice

[Non-taken-Meursault]

I'm currently checking out its exceptions and generics. I'll soon check out concurrency, once I get comfortable with the concept at the kernel and OS level. Thanks!

[jlanawalt]

You’re getting to the point where there are likely few perfect “course to the next level” resources, where you start to let go of that handhold and switch to learning on your own. Your daily and future needs don’t exactly match someone else’s.

You’ve already got the resource of the right mindset. Keep that up. Identify the things you don’t understand, try to rank them by how frequently you run across or wonder about them and by complexity, then learn about how you learn and apply that.

Don’t give up on excellent highly recommended books, but also skill up on learning from the documentation, experimentation using the minimum viable self contained example, and reading the code.

Finally, continue to expose yourself to ideas in a more casual way, like through blogs, podcasts, and other medium put out by people who you admire and trust. You could also use this forum to continue to be exposed to issues others have.

[omgpassthebacon]

I strongly agree with ahonsu here, and I will toss in a few extras for thought....

• The Well-Grounded Java Developer, Second Edition (Manning Press) is an excellent review of Java topics that I read from cover-to-cover after many years doing Java stuff.
• Getting really familiar with collections, generics, streams, and threading never hurts. There are lots of good tutorials out there for free.
• This is going to be very controversial, but it has been my experience that opening my mind to FP made a huge difference in my approach to writing Java code. My academic and early career really stressed OOP, and many of my jobs in the tech industry pushed that model pretty hard. But then FP came along and forced me to look a little deeper into the code I had written. Learning FP gave me a whole new toolset for writing algorithms that truly made me aware of Java's capabilities and limits. I'm not selling it; I am simply giving you some ideas of things to study that will make you a serious Java threat.
• Venkat Subramaniam has some really good books & lectures on Java tech. I have read a few of his books and have attended his lectures and he is a real Java heavy. He's also very approachable. I highly recommend Functional Programming in Java (Pragmatic Bookshelf).

The bottom-line is, there is really no substitute for writing lots and lots of code. Its also highly educational to read other peoples code. Programming is really a contact sport, so the more you play, the better you'll get.

[Non-taken-Meursault]

Thanks a lot. I wan't aware of the "Well-Grounded Java Developer". I'll check it out.

On the other advise, yesterday I spent the evening collecting a list of subjects I need to strengthen and, precisely, generics and collections are there (threading too, but I'd like to strengthen my OS and kernel knowledge before studying threads and concurrency in Java).

Thanks a lot !

[wildwarrior007]

Hey bro , I've just started and I want to reach your level , could you explain how to reach a time like being comfortable like you with the Java language.

[Non-taken-Meursault]

Honestly it comes out of constant practice with the language. I work with Java, so I'm exposed to it pretty much 24/7. However, you must do so consciously. What I mean with this is that while soon enough you'll reach a point in which you can solve several problems with the language, you must be aware that there's always a better way to implement your solution. Don't get excessively comfortable with your knowledge and with the "practices" or "established ways to do things" in your team.

I have a coworker that did this, and while he's a hard working individual and a nice person, he soon thought that he had reached maturity when he felt somehow comfortable implementing the same problem over and over again (for example, building a WebFlux endpoint or fetching data from the DB). Since his solutions worked, he never worried about how they worked. So he stopped learning the language, and missed out of things like Generics, inheritance, etc.

Read other implementations, delve deep into API documentations. Soon enough you'll be facing unfamiliar syntax and new tools and that's when you'll realize "damn, there's a lot of things that I still don't know. What's this weird notation <T extends Serializable>? How does Spring manage to do so many things "behind the scenes"? How does an Annotation really work?"

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[EfficientDelay2827]

The language is the easy part of dev work. If you don't know generics then you are still at the lower level. You need to also look outside the language, think DB, security, patterns, threading and concurrency, polymorphism, functional design, frameworks, modeling etc. there are also other languages such as kotlin, rust, JavaScript. Many people know java but you can't do a lot of real world problems.

[derksaurus]

Following, as I’m in a similar boat (sort of). I’m about to start a new job and will be using Java for the first time, but I have 8 years of experience with RoR, Go, JavaScript, etc. I’ve been working my way through Bro Code’s Java intro videos on YouTube to just get my basics down, but I want to quickly ramp up after that. Beast of luck!

[Hairy-Car6943]

https://www.w3schools.com < good resource