Why is this return value not of the generic type | Together Java | Page 1

astral axle Feb 16, 2023, 4:53 PM

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I don't see how it doesnt meet the requirements T does.

civic flickerBOT Feb 16, 2023, 4:53 PM

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<@&987246399047479336> please have a look, thanks.

astral axle Feb 16, 2023, 4:53 PM

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its probalby something obvious

civic flickerBOT Feb 16, 2023, 4:53 PM

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civic flicker <@&987246399047479336> please have a look, thanks.

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ancient orchid Feb 16, 2023, 4:58 PM

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astral axle its probalby something obvious

ah this is a fun one

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so the problem is that the caller specifies T

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not your code

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so like I could make a type

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enum Fuck implements IVariant { INSTANCE; }

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and call that method

astral axle Feb 16, 2023, 4:59 PM

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... why fuck

ancient orchid Feb 16, 2023, 4:59 PM

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Fuck f = GenderVariant.MALE.getDefault();

astral axle Feb 16, 2023, 4:59 PM

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wtf is this hidden message

astral axle Feb 16, 2023, 5:00 PM

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ancient orchid ``` Fuck f = GenderVariant.MALE.getDefault(); ```

how would this even be possible

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thats an illegal cast

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oh because theyre both T i guess

ancient orchid Feb 16, 2023, 5:00 PM

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try returning null from getDefault

astral axle Feb 16, 2023, 5:00 PM

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ye that works i know

ancient orchid Feb 16, 2023, 5:01 PM

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an then the Fuck code will work

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thats the problem

astral axle Feb 16, 2023, 5:01 PM

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so then how do i do this

ancient orchid Feb 16, 2023, 5:01 PM

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since the caller picks the T you can't return any T

astral axle Feb 16, 2023, 5:01 PM

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ancient orchid since the caller picks the T you can't return any T

so this whole structure isnt possible

ancient orchid Feb 16, 2023, 5:01 PM

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hmm

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good question

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idk

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just guessing

wheat pier Feb 16, 2023, 5:01 PM

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bro both of u moved threads get back here and help me!

ancient orchid Feb 16, 2023, 5:01 PM

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record Box<T>(T value) {}

astral axle Feb 16, 2023, 5:02 PM

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it works here tho

astral axle Feb 16, 2023, 5:02 PM

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wheat pier bro both of u moved threads get back here and help me!

...

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bro

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wtf

wheat pier Feb 16, 2023, 5:02 PM

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im kidding 😂

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but please

ancient orchid Feb 16, 2023, 5:02 PM

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try making it return Box<? extends Enum<?> & IVariant> getDefault()

astral axle Feb 16, 2023, 5:02 PM

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Box?

ancient orchid Feb 16, 2023, 5:02 PM

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so the caller can't pick it

astral axle Feb 16, 2023, 5:02 PM

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whats Box?

ancient orchid Feb 16, 2023, 5:02 PM

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yeah

astral axle Feb 16, 2023, 5:02 PM

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oh

astral axle Feb 16, 2023, 5:02 PM

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ancient orchid ```java record Box<T>(T value) {} ```

thats weird

ancient orchid Feb 16, 2023, 5:03 PM

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yeah

astral axle Feb 16, 2023, 5:03 PM

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what does that do

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whats the purpose of it, looks like it wouldnt rly do anythign

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nope

ancient orchid Feb 16, 2023, 5:04 PM

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astral axle whats the purpose of it, looks like it wouldnt rly do anythign

well it lets you return ? extends A & B without making a T that a called can specify

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don't have it be T

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don't use T

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just have Box<? extends`

astral axle Feb 16, 2023, 5:05 PM

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ohhhh

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forgot about wildcards

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what....

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im insane or somehting

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why does that not work

ancient orchid Feb 16, 2023, 5:07 PM

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i guess & doesn't work with wildcards

astral axle Feb 16, 2023, 5:08 PM

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shit

ancient orchid Feb 16, 2023, 5:12 PM

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yeah, & is really restricted

astral axle Feb 16, 2023, 5:12 PM

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this works

ancient orchid Feb 16, 2023, 5:14 PM

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hmm

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intrestin

astral axle Feb 16, 2023, 5:15 PM

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ok but it doesnt work for where i use it

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 static <T extends Enum<?> & IVariant> T getWithName(Class<T> instance, String name){
        return Arrays.stream(instance.getEnumConstants()).filter(t -> t.getName().equals(name)).findFirst().orElse(instance.getEnumConstants()[0].getDefault().value);
    }```

civic flickerBOT Feb 16, 2023, 5:15 PM

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astral axle ```java static <T extends Enum<?> & IVariant> T getWithName(Class<T> instance, ...

Detected code, here are some useful tools:

Formatted code

static  < T extends Enum<? >  & IVariant > T getWithName(Class<T> instance, String name) {
  return Arrays.stream(instance.getEnumConstants()).filter(t -> t.getName().equals(name)).findFirst().orElse(instance.getEnumConstants() [0] .getDefault().value);
}

astral axle Feb 16, 2023, 5:15 PM

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bruh it formatted it worse

solar light Feb 16, 2023, 6:31 PM

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yeah i dont get why the bot does that

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is it really that hard to make it not do that prompt when it detects code in ` blocks?

cloud bough Feb 16, 2023, 6:38 PM

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solar light is it really that hard to make it not do that prompt when it detects code in ` b...

in 90% of cases the prompt is helpful. in the other, click the delete button and it goes away

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if u don't want it, don't click on the format button

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that said, the prompt only triggers for OP

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not for helpers

solar light Feb 16, 2023, 6:42 PM

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cloud bough in 90% of cases the prompt is helpful. in the other, click the delete button and...

ohh, i didnt realize that was a personal message only

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whenever i had these prompts pop up in my threads i just ignored them because i wasnt entirely sure what the buttons would do

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oh actually ig its not personal? idk

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anyway they annoy me but im sure theyre a net good towards providing useful threads 🙂

astral axle Feb 16, 2023, 6:44 PM

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well tehy would be good but they dont rly format it in a good way imo

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this is split mid-method

cloud bough Feb 16, 2023, 6:46 PM

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astral axle well tehy would be good but they dont rly format it in a good way imo

in most cases they do

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they are meant for beginners who post unformatted unreadable code. which is like 80% of people posting here

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for everyone else, just click the trashbin icon and it goes away and stops annoying u

astral axle Feb 16, 2023, 6:48 PM

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oh

cloud bough Feb 16, 2023, 6:49 PM

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and because of this specific use case, it also has to yield okayish results for buggy code with syntax mistakes and non-java code.

which is why its overall quality isn't the best for rather niche Java features or edge cases

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a proper java formatter fails utterly if there's a single syntax error or when it's non-java

astral axle Feb 16, 2023, 7:06 PM

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fair

minor dew Feb 17, 2023, 5:08 AM

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why T exdends Enum<?> and not T exdends Enum<T>

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enums are self-types

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if you want this to be a polymorphic method, turn your interface into a self-type too

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implements IVariant<GenderVariant>

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and interface itself is interface IVariant<T extends Enum<T> & IVariant<T>>

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this way, you can remove all the generic declarations from your method

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although, what's the point of that since it would be an instance method anyway

astral axle Feb 17, 2023, 3:16 PM

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minor dew enums are self-types

i ended up changing it it now works, and is waaaaay simpler

#Why is this return value not of the generic type