Why can not I add an object of type Object into a List<?>?

Question

As far as I understand a List is definds as a list of some specific , yet unknown type . So whatever is the parameter type of this List

Answer 1

"?" is called WildCard Capture which means type parameter matches an Unknown Type. This means

 List listObj = returnSomeList(); 

is a list of

 Unknown Type 

and you are trying to add an Object into a List of

  Unknown Type.

The example posted by you will give you compile time error.