"Non-static method cannot be referenced from a static context" and Unbounded wildcard

Asked Jan 07 '22 at 17:03

Active Jan 07 '22 at 17:03

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There are several threads regarding:

Non-static method cannot be referenced from a static context

but the question here is a bit different. I noticed that with raw type I don't get this compilation error. On the other hand if I use the wildcard I get the error. Here the code I'm talking about:

Map<Class<? extends MySuperClass<?>>, List<MySuperClass<?>>> groupedSubClasses = 
    ids.stream().collect(groupingBy(MySuperClass::getClass));

This code won't compile because of the above error. Instead:

Map<Class<? extends MySuperClass>, List<MySuperClass>> groupedSubClasses = 
        ids.stream().collect(groupingBy(MySuperClass::getClass));

will compile.

So what is the "relation" between this error and raw type/wildcard?

asked Jan 07 '22 at 17:03

SGiux

Is `MySuperClass` a “top level” class? A single raw type will cause all generics to be removed so the reason it compiling may be less obvious than it seems. – Boris the Spider Jan 07 '22 at 17:15
Yes is an abstract top level class – SGiux Jan 07 '22 at 17:18
https://stackoverflow.com/questions/2770321/what-is-a-raw-type-and-why-shouldnt-we-use-it – abler98 Jan 07 '22 at 17:29

"Non-static method cannot be referenced from a static context" and Unbounded wildcard

0 Answers0