In the allowed assignments between superclass and subclass variables, the subclass object is an object of its superclass.

Assigning a subclass reference to a subclass variable is pretty straightforward.

The superclass variable can be used to refer only to subclass members.

Java compiler will report errors if the code refers to subclass only members through the superclass variable. 

Assigning a subclass reference to a superclass variable is safe.

Assigning a superclass reference to a superclass variable is pretty straightforward.