Java 21 Is Good?! | Prime Reacts

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[kidek]

I love hearing about new Java features while still being stuck on Java 8.

[Sam-cymv]

I worked at Google, everything was Java 8. I worked at Amazon... hell i worked on some stuff that was still Java 7. Both of those teams worked on core services. Java is proof that the syntactic sugar that devs get hyped about means very little, the value of a language is in its stability over the long haul

[lennarth.]

This feels like when a child gives you a drawing and you have to act as if you like it. Except the child is almost 30 and you hate it

[benderbg]

That's the whole point of Java, slow and steady and the reason why enterprise loves it so much. Ecosystem built on top of it solves all the business problems. You dont have to relearn 30% of language each year just because hot and popular languages like to bloat themselves with each new release. Constant changes and features != stability.

[gavinh]

8:30 - It lets you do pattern matching similar to rust. It turns the interface into a tagged union.

[fischi]

honestly, I think most people when they think of java, they think about how they feel while using it, but truth being told, I think for an enterprise, java is one of the best languages out there. It's stable, it has tons of support, it generally is less verbose than people make it to be and most importantly, it's quite consistent on how you can resolve an issue. If you open 50 classes, 80-90% of them look exactly the same. If I get a node express server for instance, I'm pretty sure that on 10 projects I'll have 15 different implementations (which is not bad per se, but if you need to switch out the people who work on it somewhat regularly that's bad)

Virtual threads remove the "color" of the functions, the same function could be blocking or not depending on where it runs, and that is amazing. There are no "async", "suspend", "callbacks" ...

[KoboldAdvocate]

As a forced java dev, it's nice to see Java catching up to C#

[nviorres]

Fair enough but you are missing the point of Loom. They didn't just implement green threads, they did it while keeping compatibility with the language's existing Thread/Concurrency/blocking APIs. That's a significant achievement IMO.

[renatocustodio]

This article didn't really show how awesome loom is. It's way better than pretty much everything else in other ecosystems.

[sinom]

While this says "Java 21" this is actually a list of a bunch of features that have been added between Java 8 (the last LTS version most people were using) and Java 21 (the at the time of writing newest version)

[loic.bertrand]

Some of the examples given here are quite bad in my opinion ^^
1:04 You don't need to use stripLeading() with text blocks, leading spaces are already stripped by the compiler.
2:41 They only put one field in the first record example, a better example would be `record Person(String name, LocalDate birthday) {}`.
12:46 I don't know why they've put a separate instanceof above the switch...
20:39 You don't need to nest try-with-resource statements, you can declare multiple resources inside the parentheses.

[yeshengwei]

No doubt you are a good programmer. However, it seems your attitude in analyzing Java 21 is not that serious and very biased since before reading the article. And to be honest, although you had used Java for sometime, I don't think you know Java so well now.
I started with C & C++, and then switched to Java since JDK 1.4.1. In recent few years, I learnt Go, JavaScript, TypeScript, and Rust. Well, Rust is a very powerful programming language with a lot of good new concepts. However, for my new server-side e-Commerce Big Data Analysis project, I still chose Java because I consider it the best choice after comparing with all the other languages I mentioned above. If my project is an Operating System, a Real-time System, or a hardware related application, then, I will probably choose Rust.
Even though Java code is a bit longer than Go or Rust with boilerplates, in my point of view, it's the easiest to read and manage language for large-scale enterprice application development among members of a big team. With modern IDEs (e.g. IntelliJ IDEA), a longer code with boilerplates does not cause longer time to write at all.
In your video, you hardly spent any time in analyzing the Virtual Threads (and did not cover Structured Concurrency at all), which for me are the most attractive 2 features in Java 21.

[CallMeKeule]

sealed interfaces really work well for ADTs (Algebraic Data Types) as well as messaging interfaces, where you want to have a determined (closed) protocol of message types.

[CheaterCodes]

The sealed classes are basically the equivalent to tagged unions; you would use them like you would use enums in Rust. Since this isn't really OOP, it feels out of place in java, but I honestly really enjoy it whenever I'm forced to use Java.

Integer divides can overflow: A signed byte is between -128 and +127 (inclusive). Therefore, dividing -128 by -1 results in an overflow.

[heeerrresjonny]

Java's slower pace at adopting some things is kind of a benefit tbh. It can sit back, wait until something catches on, then add it while remaining stable & consistent. You don't want to add something to Java only to have it fall out of favor in a year because then you end up either having to maintain support for this thing almost no one is using (creating more opportunity for bugs, vulnerabilities, etc...) or you end up breaking a bunch of stuff when you deprecate it and rip it out of the language.

[Jebusankel]

The nested trys at 21:30 aren't necessary. A try-with-resources block can handle multiple resources. Also try-with-resources isn't remotely new, it's been there since Java 7. The first part of the article that mentioned it was just about the HttpClient class implementing it, which is weird because that came out in Java 11.

[freeideas]

You guys are vastly underestimating the coolness of virtual threads. This gives us the efficiency of async/await without the complexity. With async/await, you have to say something like, "tell B to call C when B is done, tell A to call B when A is done". In java, you can just say "do A, then do B, then do C", and get the same performance.

[Bolpat]

10:45 You missed the whole idea of this. Java still has so-called open interfaces (those that you all know); they added the sealed ones to give devs a new thing in design space: It allows exhaustive switch statements; it’s a lot like enum conceptually, except that enums only has fixed objects . When you add another Animal, you want to update the switch statements. You have to update the _Animal_ interface so the switch notices that something is missing.

[TheMohawk]

Sealed interfaces are really useful for cases where e.g. you are creating a library with a bunch of types that you do not want to expose to the user (e.g. just for the sake of simplifying the library's interface for users). So, you can expose an interface instead which your 'internal' types implement. But, your library might still be dependent on the specific implementations to behave a certain way, and there is no way to restrict the interface to force implementers to honor the contract (simple example: a method should always return a positive int). In other words: This interface is not meant to be implemented by random users.

To show that the interface is not intended to be implemented, and to prevent weird issues where a user implements the interface but does something crazy which breaks your library code, you can make the interface sealed and only permit your library's own types to implement it.

The bi-directional dependency might seem weird, but sealed types are really only meant to be used within a unit of control. e.g. a module/package or within a class (for nested classes the 'permits' clause is not even required)