Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

The Java type system is broken

wouter.coekaerts.be

Post reply on HN
Print view View original

111–120 of 168 posts

Re: The Java type system is broken

#111

Post by AnimalMuppet »

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…

That would solve the problem with adding generics, yes. It would also destroy the thing people appreciate about static typing - that you get told at compile time when you've done something wrong.

Re: The Java type system is broken

#112

Post by spencerg12 »

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.

Java has been and will continue to be a contentious language - as long as programmers identify as X programmers or Y programmers.

Re: The Java type system is broken

#113

Post by hinkley »

moron4hire wrote: post #23
TazeTSchnitzel wrote: post #5

My favourite feature of Java's type system is that, because any object type also accepts null, the type system is unsound and you can convert anything to anything else: https://raw.githubusercontent.com/namin/unsound/master/doc/u...

It should be noted that soundness is not a common feature for type systems in the wild. It sounds kind of scary, "X programming language's type system is unsound", but that's pretty much been the status quo for most of programming.

Our intuition about inheritance is pretty much all wrong.

I make analogies to taxonomy because before I learned software a biology teacher told me that taxonomy is also broken, so when I learned type theory it felt like a similar kind of broken.

We think putting wings to a mammal is adding behavior, when in fact it is subtracting it. Adding wings on a mammal means you have a bat, or a flying squirrel.

You have narrowed the potential of this type, not enhanced it. Anything else a mammal might do that bats can't? You've taken all of that away. Mammals with fly() aren't the fastest land animals. They don't have the record for holding their breath, or hibernation time. They can't dive(), speak() or useTool(). Really they're kinda useless except for vermin control.

Re: The Java type system is broken

#114

Post by dlubarov »

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 .

Another flaw we can abuse is Java's covariant array types:

    Object[] objects = new Integer[] {1, 2, 3};
    objects[0] = "hello";
Also compiles but fails at runtime.

Re: The Java type system is broken

#116

Post by moron4hire »

hinkley wrote: post #113
moron4hire wrote: post #23

Earlier quoted context omitted.

It should be noted that soundness is not a common feature for type systems in the wild. It sounds kind of scary, "X programming language's type system is unsound", but that's pretty much been the status quo for most of programming.

Our intuition about inheritance is pretty much all wrong. I make analogies to taxonomy because before I learned software a biology teacher told me that taxonomy is also broken, so when I learned type theory it felt like a similar kind of broken. We think putting wings to a mammal is adding behavior, when in fact it is subtracting it. Adding wings on a mammal means you have a bat, or a flying squirrel. You have narrow…

This is probably why it's important to not anthropomorphize your code. Code abstractions do pretty much one thing: they prevent the duplication of code. They each do this in their own ways that make certain deduplications easier than others. If you focus on that, the broken analogy of taxonomy doesn't matter, and you can easily hop between the religious war camps of "OOP vs FP" and "Inheritance vs Composition". Figure out what you want your ergonomics to be and just go with that.

Re: The Java type system is broken

#117

Post by leshow »

MaxBarraclough wrote: post #70
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.

> If Java had generics in the beginning, it would look a lot different and the type system would be more powerful and safe. And conceivably a good deal faster, too. My understanding is that the JVM is required to constantly perform runtime type checks.

and pointer chasing too right? unless the runtime can optimize, every generic sits behind a pointer.

Re: The Java type system is broken

#118

Post by jerf »

kjeetgill wrote: post #58
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 ;-)

I think it's just a knee jerk reaction to some academic/PL theory types that chime in with a "Huzza! Long live (Haskell/Scala/Ocaml/etc.)!" As if a lack of soundness is dawning on anyone and was anyone's issue to begin with. It's pretty dramatic so it gets met with preemptive defensiveness. From the end of article: Everything is broken. Everything is fine.

In theory, as soon as a type system is unsound, it is unsound.

In practice, there are ranges of brokenness. If you have to go hunting for the problem, and it takes a combination of 5 obscure features which nobody would ever use together, it's not that big a deal. If it's the sort of thing that you encounter in any non-trivial program, well....

... your language dies.

Part of the reason so many people in this thread can be cavalier about type soundness issues is precisely that all the languages they use, being the languages that did not die because they have a crappy type system, are pretty sound, within the model the language is operating under, so, yeah, of course it doesn't look like a problem to a normal programmer, because it was solved a long time ago. Doesn't mean it's a bad idea, or that people should just sneer contemptuously at the issues and snidely dismiss them as academic frippery, because then these people go on to write new languages that have these sorts of issues.

(Like the recent wave of "event based" programming environments that just threw away the benefits of structured programming, because they were so thoroughly immersed in a structured programming world they didn't even realize how thoroughly they'd internalized it, had no idea what the preconditions were for it, and not only had no idea they were throwing it away but snidely berated people who pointed it out. And then spent 5+ years rediscovering it all over again....)

Re: The Java type system is broken

#119

Post by mnd999 »

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.

Except they didn’t - they introduced annotations at the same time and bumped the class file version for that.

Re: The Java type system is broken

#120

Post by icedchai »

MaxBarraclough wrote: post #70
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.

> If Java had generics in the beginning, it would look a lot different and the type system would be more powerful and safe. And conceivably a good deal faster, too. My understanding is that the JVM is required to constantly perform runtime type checks.

Good deal faster? I seriously doubt it. My understanding are generics are purely a compile time feature and does not effect run time.

I remember Java before generics: tons of casting from Object. The compiler is doing the same thing.

Post reply on HN