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Project Valhalla, Explained: How a Decade of Work Arrives in JDK 28

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Re: Project Valhalla, Explained: How a Decade of Work Arrives in JDK 28

#71

Post by bishabosha »

layer8 wrote: post #15

> But careful: == looks at internal state, which isn’t always what the object represents, so for “is this the same data” comparisons keep using equals. So == for value classes will basically be like memcmp() . That is a bit unfortunate, as it breaks encapsulation, exposing implementation details. Client code can use this to do case distinctions based on how a given value is internally represented. In a way, it’s wors…

the whole point of value class is that they should not encapsulate state, i.e. its a totally transparent data holder

Re: Project Valhalla, Explained: How a Decade of Work Arrives in JDK 28

#72

Post by gf000 »

ahoka wrote: post #70
gf000 wrote: post #39

Earlier quoted context omitted.

Sealed classes/interfaces and records are proper sum and product types. The stdlib's Option type predates this language update by a long shot, so it doesn't use sealed classes, but it is now possible to have the usual FP "Maybe" type in Java: ``` sealed class Maybe permits Some, None { record Some (T obj) {} record None() {} } ``` (You will probably have to write Maybe.Some and I might have messed up the generic synt…

Or just do as Kotlin and embrace null, but in a type aafe way.

"Funnily", having nullable types be practically `T | Null` gives you union types, not sum types (the latter is, importantly are a disjunct union!)

The main difference is that (T | Null) | Null = T | Null, while Maybe> is different from Maybe

Re: Project Valhalla, Explained: How a Decade of Work Arrives in JDK 28

#73

Post by Someone »

rf15 wrote: post #14
andyjohnson0 wrote: post #12

Earlier quoted context omitted.

> The whole attitude and process around this and the other topics gives me very little faith that Java can be steered in a sensible direction here. I agree. The stewardship of Java seems rather lacking - particularly when compared to that of .net, where MS etc. mostly seemed to make the correct decisions from the start. Does Java even have any value or mindshare at Oracle nowadays? The company seems to be a datacentr…

How .net got so many things right where java did not is a mystery to me, but appreciated (it has its own flaws, of course). Java, in my understanding, is still of core relevance to Oracle, and tied into a lot of contracts that require very little effort from them to maintain. But you are correct in observing that they want to be a datacentre/compute business more and more these days; they may have in fact overcomitte…

> How .net got so many things right where java did not is a mystery to me

Part of the reason for that is that Java is older. https://en.wikipedia.org/wiki/C_Sharp_(programming_language)...:

“In interviews and technical papers, he has stated that flaws in most major programming languages (e.g. C++, Java, Delphi, and Smalltalk) drove the fundamentals of the Common Language Runtime (CLR), which, in turn, drove the design of the C# language.”

Also, some of Java’s design warts may be there because Java was initially envisioned for much smaller devices.

Re: Project Valhalla, Explained: How a Decade of Work Arrives in JDK 28

#74

Post by [deleted] »

rf15 wrote: post #14
andyjohnson0 wrote: post #12

Earlier quoted context omitted.

> The whole attitude and process around this and the other topics gives me very little faith that Java can be steered in a sensible direction here. I agree. The stewardship of Java seems rather lacking - particularly when compared to that of .net, where MS etc. mostly seemed to make the correct decisions from the start. Does Java even have any value or mindshare at Oracle nowadays? The company seems to be a datacentr…

How .net got so many things right where java did not is a mystery to me, but appreciated (it has its own flaws, of course). Java, in my understanding, is still of core relevance to Oracle, and tied into a lot of contracts that require very little effort from them to maintain. But you are correct in observing that they want to be a datacentre/compute business more and more these days; they may have in fact overcomitte…

[deleted]

Re: Project Valhalla, Explained: How a Decade of Work Arrives in JDK 28

#75

Post by pron »

andyjohnson0 wrote: post #12
rf15 wrote: post #4

I appreciate the hard work that went into the things that did make it into Valhalla eventually, but: > The model was powerful, but also mentally heavy No it isn't! it is this interpretation that kills off the null-safety debate entirely. Saying you have a variable that cannot be null is not a mentally taxing distinction, especially since everything is labelled thoroughly. > The team, faithful to the lesson “simplify…

> The whole attitude and process around this and the other topics gives me very little faith that Java can be steered in a sensible direction here. I agree. The stewardship of Java seems rather lacking - particularly when compared to that of .net, where MS etc. mostly seemed to make the correct decisions from the start. Does Java even have any value or mindshare at Oracle nowadays? The company seems to be a datacentr…

First, your parent comment misunderstood what the section they were critiquing is referring to. It's not about nullability (which is orthogonal) but about reference/value projections.

Now, as a member of the Java team (although I'm not directly involved in Valhalla), I'm obviously biased so let me just say that both designers and fans of programming language features would do well to remember two things:

1. Opinions about features are almost never universal, even among experts, and almost each of them is about a tradeoff where different people prefer different sides. It is rare that some scientific study settles the issue.

2. These preferences are often not evenly split. Even when both sides are equally confident that their preference is the right one, sometimes 80% or 90% of programmers share a preference. The people with the strongest opinions are more often than not in the minority, because most programmers don't think so much about the programming language (nor, I would say, should they).

All of the language differences between .NET and Java fall in this "non-consensus" zone, and at least in one area I was deeply involved with, virtual thread, I can say that we thought that whatever we do we mustn't do what .NET did and that what they chose didn't work out well for them at all.

Re: Project Valhalla, Explained: How a Decade of Work Arrives in JDK 28

#76

Post by DarkNova6 »

usrusr wrote: post #31
layer8 wrote: post #15

> But careful: == looks at internal state, which isn’t always what the object represents, so for “is this the same data” comparisons keep using equals. So == for value classes will basically be like memcmp() . That is a bit unfortunate, as it breaks encapsulation, exposing implementation details. Client code can use this to do case distinctions based on how a given value is internally represented. In a way, it’s wors…

Value types are a concept very far away from the "magic black box organism" school of OOP thinking. It's not a novel way of doing classic OOP (does anyone still do that?), it's a way for a language born in OOP ideology get one step further into the post-OOP world.

Not if you do DDD where a calue type has exactly those semantics and for record types this is actually a free lunch.

Re: Project Valhalla, Explained: How a Decade of Work Arrives in JDK 28

#77

Post by DarkNova6 »

torginus wrote: post #5

I know its a faux pas in the Java world to acknowledge the existence of .NET, but how does this differ from .NET structs? Value types, generic specialization, boxing - a quick skim makes it looks like they picked the same choices.

C# actually has a fair amount of gotchas and Java aims to make these explicit. So where C# mostly copied C from a low level perspeCtive, the Java guys approached this high level and analyzed in detail which constraints give you what kind of benefit.

So where in other languages, the struct/class taxonomy is binary, Java allows more granular control, reflection the semantics of the underlying domain. Snd as it turns out, structs have a wide range of footguns, especially in a parallel context.

Re: Project Valhalla, Explained: How a Decade of Work Arrives in JDK 28

#78

Post by DarkNova6 »

torginus wrote: post #8
rf15 wrote: post #6

Earlier quoted context omitted.

Functionally they don't - java is just catching up with (by now) ancient practice. The false dichotomy of > A struct in C# has identity and mutation, so the semantics of copying on assignment or passing have to be precisely defined, which gives a heavier model for the programmer and less freedom for the runtime. Doesn't really match with what they're describing. While yes, it will not have identity in a java class re…

I don't wanna badmouth Java people, but how they push the idea that this thing is some sort of genuine breakthrough that took multiple PhDs years of cutting-edge research to implement, when in fact they basically copied what .NET did from basically year 1, is not a good look. Again, not trying to turn this into a .NET vs Java thing, I'd have been much happier if they reached some new and interesting conclusions.

The article is shit, the actual concept and roadmap goes well beyond the capabilities of C# or the CLR.

Re: Project Valhalla, Explained: How a Decade of Work Arrives in JDK 28

#79

Post by imtringued »

rf15 wrote: post #4

I appreciate the hard work that went into the things that did make it into Valhalla eventually, but: > The model was powerful, but also mentally heavy No it isn't! it is this interpretation that kills off the null-safety debate entirely. Saying you have a variable that cannot be null is not a mentally taxing distinction, especially since everything is labelled thoroughly. > The team, faithful to the lesson “simplify…

Yes, in this respect Java is 100% doomed. They've made a terrible decision and they're sticking with it for the sake of "consistency".

Re: Project Valhalla, Explained: How a Decade of Work Arrives in JDK 28

#80

Post by toyg »

Someone wrote: post #73
rf15 wrote: post #14

Earlier quoted context omitted.

How .net got so many things right where java did not is a mystery to me, but appreciated (it has its own flaws, of course). Java, in my understanding, is still of core relevance to Oracle, and tied into a lot of contracts that require very little effort from them to maintain. But you are correct in observing that they want to be a datacentre/compute business more and more these days; they may have in fact overcomitte…

> How .net got so many things right where java did not is a mystery to me Part of the reason for that is that Java is older. https://en.wikipedia.org/wiki/C_Sharp_(programming_language)... : “In interviews and technical papers, he has stated that flaws in most major programming languages (e.g. C++, Java, Delphi, and Smalltalk) drove the fundamentals of the Common Language Runtime (CLR), which, in turn, drove the desi…

This. C# was basically always meant to be "Java but done right". It came several years later, after Microsoft was legally barred from "EEE"-ing Java and required a direct competitor.
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