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The Java type system is broken

wouter.coekaerts.be

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Re: The Java type system is broken

#101

Post by pjmlp »

monocasa wrote: post #78
pjmlp wrote: post #75

Earlier quoted context omitted.

The missing part every time this story gets told, is that Microsoft already had a generics implementation ongoing being lead by Don Syme of F# fame. They just decided to release 1.0 without generics, instead of waiting for it to be 100% ready. As Don clearly describes on his blog.

Sure, totally. In fact, I'm a big fan of how Microsoft does versioning, supporting previous versions, but releasing major versions with backwards incompatible changes. You see this in DirectX, and IMO, that's why we're talking about DirectX and Vulkan, rather than AZDO OpenGL these days. It really gives you an opportunity to clean up the cruft.

Yeah, although I think they missed an opportunity to move beyond "only C goes" mindset at Khronos.

Re: The Java type system is broken

#102

Post by emodendroket »

ilikehurdles wrote: post #99
emodendroket wrote: post #51

Earlier quoted context omitted.

Whoever you are, analogies can help clarify your thinking. A type system that prevents some errors is not without value just because it cannot catch others. If the uncaught types of errors are rare and the type system that would solve them somehow burdensome it may even be a reasonable compromise to accept these faults.

Of course. At this point I'm not sure what this has to do with the code snippet mentioned upthread or the response to it. Your analogy didn't really convey why you'd think java allowing "String s = gridWrapper.get(0).get(0).get(0);" is a good vs bad thing, it just tells me that types don't protect you from everything, I think. I didn't find that the analogy added anything valuable and instead kind of simplified a pro…

I was replying to someone implying that the type system was useless because it was not ironclad.

Re: The Java type system is broken

#103

Post by alexeiz »

monocasa wrote: post #50
mcculley wrote: post #44

The mess that is the current Java type system makes me skeptical when proponents of languages like Go say not to worry, that generics can be added later. If Java had generics in the beginning, it would look a lot different and the type system would be more powerful and safe.

Unlike Java, Go doesn't have to worry about bytecode backwards compatibility. That was the main issue that had them reaching for type erasure. Take a look at C# which added it without many issues (because they were willing to break back compat of their bytecode). Go fits this model a whole lot better.

> Take a look at C# which added it without many issues

I wouldn't say "without many issues." It took a major surgery in the CLR codebase to add generics. The difference between CLR 1.1 without generics and CLR 2.0 with generics was huge. No area of code was untouched.

Re: The Java type system is broken

#104

Post by BonesJustice »

hyperpape wrote: post #17

Here's another fun trick, though it's probably not a flaw in the type system: https://twitter.com/joshbloch/status/1018987317489426432 .

Yeah, compound types like that are a bit of a hack. During type erasure, the type variable gets reduced to its leftmost type (in this case, `String`), so the `main` signature ends up being a valid entry point. Best the compiler can do to enforce the right-hand type constraints is to insert cast instructions where values are used as insances of those types.

As the tweet shows, you still get (some) type safety from the runtime checks.

Re: The Java type system is broken

#105

Post by kazinator »

Disagree with bullshit term: heap pollution.

Pollution is the proliferation of superfluous objects creating some sort of undesirable mixture. For instance "namespace pollution".

An inconsistency between the run-time type of an object in the heap, and the type of the expression in the program which refers to that object, isn't a good fit for the word "pollution".

Quit trying to pollute the computing lexicon with nonsense.

Re: The Java type system is broken

#106

Post by [deleted] »

bad_user wrote: post #28

It’s pretty tragic how people respond to such criticism emotionally, instead of acknowledging the issues and working towards fixing them or educating others in the traps and compromises involved. HN is less prone to toxicity, but this is reminiscent of Reddit and it drives away the people that want to help. As a piece of advice, some type theory never harmed anyone ;-)

[deleted]

Re: The Java type system is broken

#107

Post by hota_mazi »

kjeetgill wrote: post #48
mcculley wrote: post #44

The mess that is the current Java type system makes me skeptical when proponents of languages like Go say not to worry, that generics can be added later. If Java had generics in the beginning, it would look a lot different and the type system would be more powerful and safe.

Interesting. How do you think it would be different? I ask because the go-to is usually genetics erasure. Do you think more could or would have been different? For what it's worth, Brian Goetz doesn't see type-erasure as a such a failure and defends the design choice[0]. [0]: https://m.youtube.com/watch?v=TkpcuL1t1lY

Actually, most people who actually understand in depth the subject and the trade offs of erasure versus reification squarely side on the erasure side.

Erasure is the safest way to implement generics for a long list of reasons. Reification comes with a lot of downsides, which is why most languages that support parametric polymorphism use erasure.

Re: The Java type system is broken

#108

Post by _skel »

tabtab wrote: post #77
mcculley wrote: post #44

The mess that is the current Java type system makes me skeptical when proponents of languages like Go say not to worry, that generics can be added later. If Java had generics in the beginning, it would look a lot different and the type system would be more powerful and safe.

Just use dynamic or better yet type-tag-free languages. Types are hard to get right and hard to reason about. Sure, there are some Sheldons out there who master it even under pasta applications, but most of us are not Sheldons. C# also bleeped up types by adding nullable types, making reflection into a scavenger hunt. For dynamic or tag-free languages, type indicators could be used to parse-check scalar (base) values…

I prefer my type errors at compile time.

You have to reason about types in any language because passing the wrong type to a function can result in errors. You have to do all of that mental work by yourself in a dynamic language because there isn't a system to do it for you.

Re: The Java type system is broken

#109

Post by cs02rm0 »

bunnymancer wrote: post #56
MrBuddyCasino wrote: post #37

> Everything is broken. Everything is fine. This is the correct conclusion. The people getting outraged over this are the same that will hold long and boring monologues about how everybody does REST wrong.

Had a client just last month that were doing SOAP wrong somehow... Required a SOAP message, that contained no XML after the message tag, but instead the entire message body was to be a JSON, and responded with a JSON if something was wrong, and a fully formed SOAP message if things were Ok. That and the guys that handle your money use the Http status code as their personal error messages. Except when the error is on…

Had a client just last month that were doing SOAP wrong somehow...

To be fair, I'm not sure there's any other way.

Re: The Java type system is broken

#110

Post by aserafini »

bunnymancer wrote: post #56
MrBuddyCasino wrote: post #37

> Everything is broken. Everything is fine. This is the correct conclusion. The people getting outraged over this are the same that will hold long and boring monologues about how everybody does REST wrong.

Had a client just last month that were doing SOAP wrong somehow... Required a SOAP message, that contained no XML after the message tag, but instead the entire message body was to be a JSON, and responded with a JSON if something was wrong, and a fully formed SOAP message if things were Ok. That and the guys that handle your money use the Http status code as their personal error messages. Except when the error is on…

I'm guessing you're talking about Adyen. At least I've had exactly the same experience integrating with their API. It's an awful mismash. I even get responses with bool = 'true' in their json, but only sometimes. That's the string 'true' sometimes and othertimes json true.
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