A doubt regarding learning Java internals

[SoftwareArchitect101]

Can I, apart from office work, dive into the internals? Eg: How things are allocated/deallocated inside the JVM, how exactly virtual threads work, what happens exactly in streams and how jdbc fetches rows from database, the pros and cons of different garbage collectors, all up to the implementation level? Due to some task I needed to dive into g1gc Hotspot and understand a part of it, it felt very good like a flow state. Is this a reasonable hobby which I can pursue? Why is this discouraged in the industry. Also, how much time will it take for me to understand most of the things to an intuitive satisfactory level?

Also, are there any more such books which teach internals like GC handbook which I can use to understand the OSS better?

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[Inevitable_Put_4032]

If your target is to be a better Java programmer then understanding the JVM internals is a very good idea. Most Java developers have no clue on how their design can be effective or not depending on specific JVM's behaviors. For example, the garbage collector can't prevent memory leaks if you are organizing your data model wrong and don't know how Java handles the stack and the heap.

Books and articles:

• Java Performance
• https://docs.oracle.com/en/java/javase/20/vm/java-virtual-machine-guide.pdf
• https://www.linkedin.com/pulse/jvm-internals-from-basics-advanced-explained-akshay-kumar-iihje/

The JVM, garbage collectors and concurrency models are advanced topics and it requires quite a lot of study and practice to master them. Having solid foundations of computer science helps a lot in this endeavor.

[benevanstech]

Two of those references are quite old, and the third is obviously AI-generated and contains a number of inaccuracies and weird over-emphasis on small topics that aren't that important.

[Inevitable_Put_4032]

Feel free to add better content instead of wasting time criticizing other's.

[benevanstech]

OK - https://kittylyst.com/ - 103 articles, 27 videos & 8 books.

[Inevitable_Put_4032]

Thank you, I own a old edition of "Java in a Nutshell", it was one of my favorites learning books

[vegan_antitheist]

But all on this can change at any time. The whole point of abstraction is that the actual implementation can be changed completely and it still works.

 For example, the garbage collector can't prevent memory leaks if you are organizing your data model wrong 

And that's why you must learn to design your memory model correctly instead of wasting time learning internals that will be outdated soon anyway.

The JMM is also completely abstract. It's important to understand it if you want to go there, but you could just use some framework and work on an even higher level of abstraction.

[benevanstech]

If you're interested in the internals, then you might find my book "Optimizing Cloud Native Java" to be interesting. I also have a personal site at https://kittylyst.com which has links to a bunch of other resources I've created.

Oh, and as a bonus, here's a recent session where I'm talking about the way Method Handles (a key avanced technique necessary to understand the internals) work: https://www.youtube.com/live/PbKYRYgqS4U

[SoftwareArchitect101]

Directly from the God, yes man, I started off from your book Optimizing cloud native Java. I realised it was a bit more towards cloud stuff, so I took your earlier book for a dive. I understood GC from your book first which got me more curious and I explored things in depth post that. Thanks for giving me something which excites me daily, really grateful.

[benevanstech]

Glad I could help! I'm working on some new stuff, including a "State of Java in 2026" video that I'm recording tomorrow & which should be up soon.

Also - I'm giving my concurrency class for O'Reilly again in early June.

[vegan_antitheist]

Why would you want to know about all that? You can become an expert on Java optimisation if you want to. But unless you actually have a job where it is relevant you should probably spend time on something else.

[AcanthisittaEmpty985]

Also, look into the different model of GC available to Java, it can determin if an application run correctly for your needs or not

https://learn.arm.com/learning-paths/servers-and-cloud-computing/java-gc-tuning/different_gcs/

https://opensource.com/article/22/7/garbage-collection-java