Java compiler bug with generics

Asked Apr 12 '16 at 19:06

Active Apr 12 '16 at 19:06

Viewed 42 times

a rather unusual behavior has occurred while I was using generics the other day. The compile could no longer determine properly the return type of a method inside a generic class that had a type argument.

I am basically having 4 classes:

AbstractModel, ConcreteModel, AbstractService< AbstractModel > and ConcreteService< Model >

In AbstractService I have a simple list of Longs and a method "getListOfLongs". Now something very very strange happens when I try to get my list of longs:

for(Long l : service.getListOfLongs()){

}

And java compiler tells me my list is of Objects instead of longs.

You can try the example on my github: https://github.com/sashokbg/java-bug/

asked Apr 12 '16 at 19:06

sashok_bg

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Did you file a bug report with Oracle? – Brian Knoblauch Apr 12 '16 at 19:07
not yet, I wanted to share it with you first – sashok_bg Apr 12 '16 at 19:09
Is it fixed if you declare the generic type in your method signature, e.g., `test(AbstractService> service) {` ? Mixing raw types and generics is always weird. – Darth Android Apr 12 '16 at 19:10
What IDE are you using? – Tophandour Apr 12 '16 at 19:12
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This isn't a bug. `service` is a raw type, so it's treated as if the method returns a raw `List`, not a `List`. – Paul Boddington Apr 12 '16 at 19:12
Intellij, but it is not related to the IDE. I have to try if parametrizing the service fixes it. – sashok_bg Apr 12 '16 at 19:13
@PaulBoddington Yes it is raw, but the List has nothing to do with the parametrized type. It is weird behavior for me – sashok_bg Apr 12 '16 at 19:14
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@sashok_bg It's VERY weird, I know. But trust me that really is how raw types work. All generic type information is simply ignored, even if it has nothing whatsoever to do with the missing parameter. – Paul Boddington Apr 12 '16 at 19:15
@PaulBoddington Indeed, thank for your explanation it really makes more sense now, as weird as it is ! – sashok_bg Apr 12 '16 at 19:17
No problem. Glad I could help. – Paul Boddington Apr 12 '16 at 19:18
[This is a more pertinent duplicate question](http://stackoverflow.com/questions/27314649/why-does-javac-complain-about-generics-unrelated-to-the-class-type-arguments). – Andy Turner Apr 12 '16 at 20:48

Java compiler bug with generics

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