Why can't assign I <? extends Type> to ?

Question

The following statements:

URLClassLoader ucl = (URLClassLoader) ClassLoader.getSystemClassLoader();
Class uclc = ucl.getClass();
         


        

Answer 1

Covariance vs contravariance vs invariance

• Class is invariant.

As a result,

Class is not a subtype of Class

---

In Java a variable can hold a reference of an instance of same type or subtype.

Hence,

Class uclc = ucl.getClass();

is invalid.

On the other hand,

Class uclc = ucl.getClass();

would be valid.