}In the next example, we aim a superclass reference at a subclass object. 

  §Invoking a method on a subclass object via a superclass reference invokes the subclass functionality

  §The type of the referenced object, not the type of the variable, determines which method is called

}This example demonstrates that an object of a subclass can be treated as an object of its superclass, enabling various interesting manipulations.

}A program can create an array of superclass variables that refer to objects ofmany subclass types. 

  §Allowed because each subclass object is an object of its superclass. 

}A superclass object cannot be treated asa subclass object, because a superclass object is not anobject of any of its subclasses. 

}The is-a relationship applies only up the hierarchy from a subclass to its direct (and indirect) superclasses, and not down the hierarchy.

}The Java compiler does allow the assignment of a superclass reference to a subclass variable if you explicitly cast the superclass reference to the subclass type

  §A technique known as downcasting that enables a program to invoke subclass methods that are not in the superclass.