Java中的泛型和继承问题

Question

Please, consider my code:

class A {

}

class B extends A {

}

class AWrapper<T extends A> {

}

class BWrapper<T extends B> extends AWrapper<T> {

}

So, I have C extends B etc, and CWrapper<T extends C> extends BWrapper<T> etc. Now, I use these classes this way:

class Test {

    private Class<? extends AWrapper<? extends A>> klass;//LINE X

    public Test() {
         this.klass = BWrapper.class;//LINE Z
    }
}

At LINE X I need to set different classes - AWrapper, BWrapper, CWrapper etc. However, at LINE Z I get an error. Could anyone help to fix it?

Answer 1

imho, what you are looking for is :

private Class<? extends AWrapper> klass;

even if AWrapper is raw. At least this way you could say that your parameter takes "a class that is subtype (or self) of AWrapper ". But that should be the thing you care about anyway. Generics are not preserved at runtime, so no matter what Class you have there, it is going to be without its inferred parameters.