Problem with Java generics with class

Question

Unable to determine this problem. I have these interfaces:

public interface LoadableObject
{
}
public interface LoadableObjectFactory<T>
{
}

And now I want to do this:

public class ObjectReference<T extends LoadableObject>
{
    Class<? extends LoadableObjectFactory<T>> _cls;

    public ObjectReference(LoadableObjectFactory<T> obj)
    {
        _cls = obj.getClass();
    }
}

But I get an error message:

incompatible types
found   : java.lang.Class<capture#885 of ? extends test.LoadableObjectFactory>
required: java.lang.Class<? extends test.LoadableObjectFactory<T>>
  _cls = obj.getClass();
                     ^

I can compile if I delete the param parameters for LoadableObjectFactoryin the definition _cls, but then it is an incomplete type ... Is there something that I am missing or simply impossible?

Answer 1

getClass () at runtime provides the class <? >. Due to the erasure type, general parameter information is not available. You have to throw

    @SuppressWarnings("unchecked")
public ObjectReference(LoadableObjectFactory<T> obj)
{
    _cls = (Class<? extends LoadableObjectFactory<T>>) obj.getClass();
}

to make it work

Answer 2

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Answer 3

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Answer 4

, LoadableObjectFactory :

public interface LoadableObjectFactory<T extends LoadableObject>

, - Object.getClass() , . , java.lang.Object

class Object<T extends Object<T>> {
    native Class<T> getClass();
}

java.lang.Object .