Java™ How to Program, Seventh Edition

10.3. Demonstrating Polymorphic Behavior

Section 9.4 created a commission employee class hierarchy, in which class BasePlusCommissionEmployee inherited from class CommissionEmployee. The examples in that section manipulated CommissionEmployee and BasePlusCommissionEmployee objects by using references to them to invoke their methods—we aimed superclass references at superclass objects and subclass references at subclass objects. These assignments are natural and straightforward—superclass references are intended to refer to superclass objects, and subclass references are intended to refer to subclass objects. However, as you will soon see, other assignments are possible.

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