The Java type system is broken • Hacker News Board

Re: The Java type system is broken

#11

Post by TazeTSchnitzel » Thu, Jul 19, 2018, 1:51 PM UTC

stingraycharles wrote: post #9

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...

Wouldn't that be a problem in most languages? Even Haskell allows for it through Data.Dynamic If I can serialize to String, and then deserialize a String to any type of class, I can effectively "cast" anything to anything.

By “convert” here I mean convince the compiler that any thing of type A is any type B, when it definitely isn't, without using an explicit cast.

Re: The Java type system is broken

#12

Post by agumonkey » Thu, Jul 19, 2018, 1:52 PM UTC

viach wrote: post #4

From the examples: "String s = gridWrapper.get(0).get(0).get(0);" - Java type system is broken! Java is not perfect, but this looks to me like a broken code indeed ".get(0).get(0).get(0)". Could we rephrase the message of the article as "If you write really broken code in Java, you might be not guarded by the type system". And this is, well, uhm, well... acceptable?

It's stupid code, but a type system has to be code agnostic. Otherwise you're back to dynamic languages with local type annotations.

Re: The Java type system is broken

#13

Post by Anderkent » Thu, Jul 19, 2018, 1:54 PM UTC

viach wrote: post #4

From the examples: "String s = gridWrapper.get(0).get(0).get(0);" - Java type system is broken! Java is not perfect, but this looks to me like a broken code indeed ".get(0).get(0).get(0)". Could we rephrase the message of the article as "If you write really broken code in Java, you might be not guarded by the type system". And this is, well, uhm, well... acceptable?

> And this is, well, uhm, well... acceptable?

It is not. The only purpose of a type system is to prevent broken code from compiling. When it fails to do so, it is broken.

Re: The Java type system is broken

#14

Post by nik736 » Thu, Jul 19, 2018, 1:54 PM UTC

Java is broken ¯\_(ツ)_/¯

Re: The Java type system is broken

#15

Post by bdhess » Thu, Jul 19, 2018, 1:55 PM UTC

viach wrote: post #4

From the examples: "String s = gridWrapper.get(0).get(0).get(0);" - Java type system is broken! Java is not perfect, but this looks to me like a broken code indeed ".get(0).get(0).get(0)". Could we rephrase the message of the article as "If you write really broken code in Java, you might be not guarded by the type system". And this is, well, uhm, well... acceptable?

The author is trying to write a concise example. You could achieve the same effect by writing three for loops, but that would take additional code and declarations that make his point less clear.

Re: The Java type system is broken

#16

Post by freddie_mercury » Thu, Jul 19, 2018, 1:57 PM UTC

rimunroe wrote: post #7

viach wrote: post #4

From the examples: "String s = gridWrapper.get(0).get(0).get(0);" - Java type system is broken! Java is not perfect, but this looks to me like a broken code indeed ".get(0).get(0).get(0)". Could we rephrase the message of the article as "If you write really broken code in Java, you might be not guarded by the type system". And this is, well, uhm, well... acceptable?

Is a type system really worth that much if it can't help you in a situation where your code is ugly and hard to follow?

"Is X really worth it if it isn't perfect and doesn't cover every edge case?"

I kinda feel like humanity has repeatedly decided the answer to this question is "yes".

"Being valuable" isn't binary. There are relative amounts of value, I think.

Re: The Java type system is broken

#17

Post by hyperpape » Thu, Jul 19, 2018, 1:57 PM UTC

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

Re: The Java type system is broken

#18

Post by opnitro » Thu, Jul 19, 2018, 1:57 PM UTC

viach wrote: post #4

From the examples: "String s = gridWrapper.get(0).get(0).get(0);" - Java type system is broken! Java is not perfect, but this looks to me like a broken code indeed ".get(0).get(0).get(0)". Could we rephrase the message of the article as "If you write really broken code in Java, you might be not guarded by the type system". And this is, well, uhm, well... acceptable?

Is it? The whole point of a type system is that it gives you guarantees over your code. Certain bugs should be inexpressible within the language.

Re: The Java type system is broken

#19

Post by macspoofing » Thu, Jul 19, 2018, 1:57 PM UTC

viach wrote: post #4

From the examples: "String s = gridWrapper.get(0).get(0).get(0);" - Java type system is broken! Java is not perfect, but this looks to me like a broken code indeed ".get(0).get(0).get(0)". Could we rephrase the message of the article as "If you write really broken code in Java, you might be not guarded by the type system". And this is, well, uhm, well... acceptable?

If you don't like this example, you can always find cases where the limitations of the type system (or more specifically Generics) become apparent. This isn't quite so obvious during 'normal' application development, but if you start creating libraries or frameworks and you want generic type support, you will run into a wall very quickly.

Re: The Java type system is broken

#20

Post by byte1918 » Thu, Jul 19, 2018, 1:58 PM UTC

viach wrote: post #4

From the examples: "String s = gridWrapper.get(0).get(0).get(0);" - Java type system is broken! Java is not perfect, but this looks to me like a broken code indeed ".get(0).get(0).get(0)". Could we rephrase the message of the article as "If you write really broken code in Java, you might be not guarded by the type system". And this is, well, uhm, well... acceptable?

If he were to show real world example, few would bother to follow it through because it would be tens of lines of code spanning through multiple classes and namespaces.