class parameter of generic type

Question

This code does not compile:

public static void main(String[] args) {
  someMethod(SomeInterfaceImpl.class); // Compile error
}

static <T> void someMethod(Class<? extends SomeInterface<T>> param) {}

interface SomeInterface<T> {}

class SomeInterfaceImpl<T> implements SomeInterface<T> {}

This error is shown:
The method someMethod(Class<? extends SomeInterface<T>>) in the type SomeApp is not applicable for the arguments (Class<SomeInterfaceImpl>)

I could ignore generics and annotate with @SuppressWarnings("rawtypes").

How can I change my code to be able to use this method without omitting the generics definition? Either I need to change how the method is called and provide some kind of genericified class or I need to change the method definition.

Note: `?` stands for `Object` class so based on provided information nothing can be said — bananas, Nov 25 '19 at 08:50

score 2 · Accepted Answer · edited Nov 25 '19 at 10:39

2

Possible solution

old:

static <T> void someMethod(Class<? extends SomeInterface<T>> param) {..}

new:

static <T extends SomeInterface<?>> void someMethod(Class<T> param) {..}

edited Nov 25 '19 at 10:39

Rainer Jung

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answered Nov 25 '19 at 10:03

Pshemo

122,468
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I made this answer community wiki to encourage others to add proper explanation of why solution from this answer works but OP version doesn't (currently I can't). – Pshemo Nov 25 '19 at 10:07

class parameter of generic type

1 Answers1