Java How To Program, Late Objects, 11th Edition

... relationship between subclasses and superclasses (i.e., the is-a relationship) by assigning a subclass reference to a superclass variable. This program uses classes CommissionEmployee and BasePlusCommissionEmployee from Fig. 9.10 and Fig. 9.11, respectively.

Fig. 10.1 Assigning superclass and subclass references to superclass and subclass variables.

 1   // Fig. 10.1: PolymorphismTest.java
 2   // Assigning superclass and subclass references to superclass and
 3   // subclass variables.
 4
 5   public class PolymorphismTest {
 6      public static void main(String[] args) {
 7         // assign superclass reference to superclass variable            
 8         CommissionEmployee commissionEmployee = new CommissionEmployee(  
 9            "Sue", "Jones", "222-22-2222", 10000, .06);                   
10
11         // assign subclass reference ...